Re: Topband: Hi Z amplifiers for 160m
More power to make up for my 10db excess noise = xxx Kw - whoopee! Need to get some 3 phase. Remote Rx, eg 100km makes a lot more sense. Clubs could put up shared facilities. With direct sampling synchronous receivers and down sampling of say the bottom 50Khz of 160, every user could reconstruct their own pattern out of a 4 or 8 square. Residential internet bandwidth is commonly several hundred Mbit/sec. The supercomputer on every desk is up to the arithmetic. If you live in the boonies without 200Mbit you don't need the remote Rx anyway. Just a small matter of software ;) ;) Haven't the radio telescope guys done this in GHz bands? Grant KZ1W On 3/13/2020 09:42, Jim Thomson wrote: Date: Thu, 12 Mar 2020 20:25:16 -0700 From: Jim Brown To: topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
On 3/13/2020 12:34 PM, Richard (Rick) Karlquist wrote: On 3/12/2020 4:29 PM, Mikek wrote: I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'. If anyone has an interest, I have some more files in my computer. https://www.okdxf.eu/lankford/Hi%20Z%20PPL%20Loop%20And%20Flag%20Arrays.pdf I Mikek KF4ITA _ I didn't look at this circuit carefully; Mikek pointed out that the JFET's are complementary, not in parallel. (Thanks Mikek for correcting me). I also see that Lankford writes that his circuit is derived from Trask's circuit. In any event, the following reference by Chris Trask, N7ZWY gives a bunch of different versions of this circuit. http://home.earthlink.net/~christrask/Complementary Push-Pull Amplifiers.pdf Chris points out that this idea goes back to at least 1982. Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
On 3/12/2020 4:29 PM, Mikek wrote: I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'. If anyone has an interest, I have some more files in my computer. https://www.okdxf.eu/lankford/Hi%20Z%20PPL%20Loop%20And%20Flag%20Arrays.pdf I Mikek KF4ITA _ This seems to be the same old JFET source follower that has been around forever, except it uses two FET's in parallel. Why not 3 or 4? I completely fail to see why this amp would be superior to similar designs already being widely used. Can someone enlighten me as to what is special about it, if anything? My approach to the amplifier noise issue is to abandon 102 inch CB whips, however elegant, and instead use 30 foot monopoles with top loading, as a brute force tool. MUCH more signal coming in, in the first place. Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Me neither. On Fri, Mar 13, 2020, 12:22 PM Wes wrote: > It's not clear to me. > > Wes N7WS > > On 3/13/2020 9:42 AM, Jim Thomson wrote: > > ## Clearly whats required is a long overdue increase in TX > power limits on 160 band...and also 80+40. > > That or arrl legal remote RXs. pick one. > > > > Jim VE7RF > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
It's not clear to me. Wes N7WS On 3/13/2020 9:42 AM, Jim Thomson wrote: ## Clearly whats required is a long overdue increase in TX power limits on 160 band...and also 80+40. That or arrl legal remote RXs. pick one. Jim VE7RF _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
On Thu, Mar 12, 2020, 3:48 PM Michael Tope wrote: > There are a lot of SMT to DIP adapter boards out there which would allow > newer SMD op-amps to be used in older through-hole PWB layouts. > > > https://www.digikey.com/product-detail/en/aries-electronics/LCQT-SOIC8-8/A880AR-ND/4754588 This is great advice, which I think a lot of folks are too quick to dismiss in this era of vanishing through-hole DIP ICs and transistors with wire leads. I successfully did just that with an SO-23 (VERY tiny SMD package) J310 transistor. It was not only my very first attempt at soldering with solder paste and hot air, but it was the easiest thing that I ever soldered! (And I've soldered north of two million connections.) Squirt a *small,* even line of solder paste through both rows of bright copper pads, place the SMD device onto the paste, and a heat gun from the underside of the (level) adapter board will make the solder flow exactly where it should. It'll look like it was professionally machine-soldered. FORGET trying to solder an SMD device using the regular method! Even with a bright light and a magnifying headband, it just makes a mess, pushes the SMD device around, and the solder bridges are difficult to clear. Mine did not have the DIP plugs as this one does, just holes for small wire leads. Solder paste (a powdered solder and flux mix) can be somewhat expensive, and IIRC it has a shelf life of less than 5 years. But I found a guy on eBay who repackages a big jar of solder paste into small syringes for cheap. He even included two different size nozzles. Don't know if he's still in business, but there was a nice instructional video that will make believers out of any "Well, I couldn't do that" skeptics reading this. Sorry that I don't have a link handy. Last time I looked, YouTube had several very good videos on this method of soldering. Qrz.com has threads about this method, you might search there also. Keeping the paste in your refrigerator in a small Ziploc bag will lengthen its useful life. It would take very fine wires indeed to solder small tinned wires directly to those tiny devices. Just get an adapter board. Trust me. :-) 73, Mike W0BTU _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m (LONG)
Hi Mike, Yes, the math can get tricky and cause you to get lost in the forest. I'm not afraid of doing math (I did a mathematics minor in graduate school) but as an engineer, I prefer to seek the simplest possible solutions to engineering problems. This is a case where you can avoid messy math by falling back on basic principles. First, I have invoked a passive, lossless phase combiner circuit for the array. There is no loss in generality in doing so. Gain or loss are just scaling factors that affect everything equally. This is why I said the total amplifier circuit noise power coming out of the combiner is exactly equal to the sum of the individual amplifier noise powers entering the combiner. There is no combining loss and energy is conserved. For circuit noise it doesn't matter what phases are used in the combiner because random noise is incoherent. Phase only matters for coherent signals. Next I fix the gain of a single vertical at 0 dB. Antenna gain is just another scaling factor and here were are only interested in relative gain (a single vertical vs. a phased array) when determining S/N ratios coming out of the combiner. When I say the received atmospheric power is one "atmospheric noise power unit", the gain is imbedded in that quantity but there is no need to actually calculate the absolute gain for our purposes. Next we invoke the principle that the spatially-averaged gain of a single vertical and a phased vertical array are exactly the same. This allows us to determine the atmospheric noise power coming out of the combiner without actually doing any phasing calculations. For our combiner the total combined atmospheric noise for the array is exactly the same as the total atmospheric noise received by a single vertical. For signals of interest, again we don't need to do any brute-force mathematical phasing calculations. We can fall back on antenna modeling programs. Of course you can do the math, but modeling programs will spare you the effort. Because we have already fixed the gain of a single vertical (at 0 dB), we can use EZNEC (or your favorite modeling program) to determine how much additional gain the array provides on the signal of interest, based on its direction of arrival. We have already established the array gain for atmospheric noise is the same for the array and the single vertical. Therefore the S/N improvement of the array vs. the single vertical (assuming atmospheric noise is the dominant noise) is just the difference between the signal gain of the array and the single vertical. Antenna modeling gives you that number. No ugly math is needed. Getting back to my earlier e-mail about circuit noise vs. atmospheric noise, we do need to keep track of the actual amplifier circuit noise relative to the atmospheric noise to insure that the circuit noise doesn't degrade the overall noise performance of the system. That will guide us in the design of a low-noise amplifier. To put numbers on these noise quantities, we need to either calculate circuit noise power, as others have already started to do, or to measure it (as I have done for different amplifiers). Similarly for atmospheric noise, we need to calculate it or measure it. I leave that for others to do. For an array of N amplified elements, we need to insure that N times the circuit noise power of a single amplifier remains well below the atmospheric received by the array. 73, John W1FV -Original Message- From: Topband [mailto:topband-bounces+john.kaufmann=verizon@contesting.com] On Behalf Of Michael Tope Sent: Friday, March 13, 2020 7:34 AM To: topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m (LONG) I agree with your conclusions regarding the case of isotropic atmospheric noise. This is the same reason that cold space looks like 3 Kelvin regardless of how high the antenna gain. As the antenna gain goes up you reinforce to a greater degree a lesser slice of the overall pie. This ends up being a wash. Where I think you may be mistaken, is the relationship between the number of amplified elements (N), the gain of the antenna, and properly book keeping combining losses. If I have N amplified elements and I mathematically sum the amplifiers outputs with zero combining loss (this would be equivalent to digitizing the output of each amplifier and then summing the results in digital processing), then the uncorrelated noise from the amplifiers (as you correctly point out) sum to 10*log(N). Double the number of amplified elements and you double the noise power due to the amplifiers (i.e. 3dB amplifier noise increase). So far we agree. Where it gets tricky is when you consider the mathematical addition of the over-the-air contributions. If I have a linear broadside array and I double the number of elements from N to 2*N, the mathematical sum of the components of the signal-of-interest in the bore site o
Re: Topband: Hi Z amplifiers for 160m
Date: Thu, 12 Mar 2020 20:25:16 -0700 From: Jim Brown To: topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
The document was published last year so we might assume the noise graph is up to date. To put this in perspective, To put the ITU-R P.372-14 claimed noise in perspective here's the calculated antenna terminal voltage for a 100% efficient 1/4 wavelength vertical in 500 Hz bandwidth. S-units are also shown. Quiet receiving site -- 4.7 nV/m, vert 1.3 uV, S-4 Median city noise -- 66 nV/m, vert 19 uV, S-8 Dave KH6AQ (formerly WX7G) > > > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m (LONG)
r throughput loss imparted by the combiner circuit). To determine the total atmospheric noise coming out of the combiner circuit, let's assume the atmospheric noise has a completely uniform distribution in 3-dimensional space. That is, the strength of the atmospheric noise is the same in every direction. This is an idealized assumption, but is often a reasonable approximation to reality. Under these assumptions, the total atmospheric noise out of the combiner turns out to be just one "atmospheric noise unit"! In other words, it is exactly the same as the atmospheric noise coming out of a single vertical. This is because the total atmospheric noise power picked up by the array is just the gain of the array (relative to a single vertical) averaged over all of 3-dimensional space times one "atmospheric noise unit" (the noise picked up by a single vertical). That average gain is exactly 0 dB, so the total atmospheric noise doesn't change in our idealized system. It doesn't matter what the antenna pattern is; the average gain is always 0 dB, which is why we did not need to be concerned with details of how signals are phased up to form a beam pattern. Of course, a different gain applies to actual signals that are coming from a specific direction and are not uniformly distributed like atmospheric noise, which is why we see a S/N improvement when the array is aimed at a signal of interest. So, we have demonstrated that in relative terms, the amplifier circuit noise power in an array of N amplified antennas goes up by a factor N whereas the atmospheric noise does not change. That increase in the amplifier noise contribution relative to atmospheric noise degrades the overall noise figure of the system. However, as long as we keep the amplifier noise contribution small enough, the noise figure degradation can also be kept to a minimum. That is why having more amplified elements makes it more important to design the antenna amplifiers for low circuit noise. 73, John W1FV -Original Message- From: Topband [mailto:topband-bounces+john.kaufmann=verizon@contesting.com] On Behalf Of Michael Tope Sent: Thursday, March 12, 2020 4:37 PM To: topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m Hi Lee, Yes, if you are combining coherent signals that are not in phase, then the each of the voltage vectors is weighted by cos(phi-i) where phi-i is the angle between the i-th voltage vector and the 1st vector. If phi=0, then you have the case I described previously. I can see how this can get tricky, however, with an electrically short baseline where you are striving for cancellation in the rearward looking direction. It's like you cancel in the rearward direction and almost cancel in the preferred direction :-). This degrades the SNR not because the noise is adding up, but because the signals are subtracting down. 73, Mike W4EF. _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
On 3/12/2020 7:44 PM, Dave Cuthbert wrote: Feel free to review my method/math and make corrections as needed. Didn't review your math, but the more important question is, "how old is your noise data?" In my experience trying to work EU on Topband now as compared to c.a. 2007-8 is vastly more difficult thanks to higher noise levels on both ends. Back then I could work EU on CW; now, with better antennas, I need the 10 dB advantage of FT8. In the past six seasons I've heard six EU/U.K. stations on CW, two were able to hear me. And those were all during one of this season's contest. Bottom line -- if your noise data is ten years old, I'd add 10 dB to it; if it's older, probably more. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
*Amp/antenna noise *-- is the AD8045 noise low enough for a 3-meter monopole? *0.26 uV amp noise vs. 0.16 uV man-made rural noise and 2.3 uV city with a 3-meter monopole. * Feel free to review my method/math and make corrections as needed. *Rural Noise*, ITU-R P.372-14 (link below) Working thru formula (7) on page 4 using Figure 7 the man-made noise (quiet receiving site) E-field at 1.8 MHz is *4.8 nV/m* in a 1 Hz BW. In a *500 Hz* bandwidth this is *107 nV/m*. Given that a 3-meter (circle array) monopole has an effective height of 1.5 meters the antenna terminal voltage is *0.16 uV*. Median city noise is 23 dB higher at *2.3 uV.* *Noise Calculation Inputs* 6-meter monopole source impedance -j3700 ohms AD8034 voltage noise 3 nV/Hz^0.5 @ 1.8 MHz AD8045 current noise 3.2 pA/Hz^0.5 @ 1.8 MHz, thru the 3700 ohm antenna reactance is 12 nV/Hz^0.5 Total noise voltage is the RSS of 3.0 nV and 11.8 nV = *12 nV/Hz^0.5* https://www.analog.com/media/en/technical-documentation/data-sheets/AD8045.pdf https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.372-14-201908-I!!PDF-E.pdf Dave KH6AQ On Thu, Mar 12, 2020 at 6:18 AM Dave Cuthbert wrote: > *JFET op amp vs bipolar op amps, *LTSpice simulations connected to a 3 > meter monopole > > A bipolar op amp doesn't always give the lowest noise with a short > monopole at 1.8 MHz because the op amp current noise creates noise voltage > across the antenna capacitive reactance. Additonally, op amps can be > connected in parallel for lower voltage noise at the expense of higher > input capacitance (which loads down the antenna signal voltage). > > Simulations of the YCCC amp with a bipolar op amp and a JFET op amp were > performed. Next, preamps having 2, 4 and 6 JFET op amps were modeled. As > the number of op amps goes up the antenna voltage goes down with optimum > S/N ratio, in this case, with 4 op amps. It shows 4.5 dB better S/N than > the bipolar op amp. The bipolar op circuit is modeled with an LTC6228 > rather than an AD8045 because I didn't have to import the AD8045 model into > LTSpice. I can try to import the AD8045 later if anyone is interested. The > LTC6228 op amp has 1/3 the voltage noise and the same current noise with > Bias Current Compensation disabled, so it should show lower noise than the > AD8045. The JFET op amp is the ADA4637 and IMD simulations were run with it > looking better than the bipolar. > > > *YCCC amp with bipolar vs JFET op amp for a 3 meter monopole at 1.8 MHz* > LTC6228 bipolar op amp, 9.5 nV/Hz^0.5, loaded sig 0.93, relative S/N ratio > 0 dB > ADA4637 JFET op amp, 6.7 nV/Hz^0.5, loaded sig 0.85, relative S/N ratio > 2.2 dB > 2 X JFET op amp, 4.8 nV/Hz^0.5, loaded sig 0.74, relative S/N ratio 3.9 > dB > 4 X JFET op amp, 3.6 nV/Hz^0.5, loaded sig 0.59, relative S/N ratio *4.5 > dB* > 6 X JFET op amp, 3.1 nV/Hz^0.5, loaded sig 0.49, relative S/N ratio 4.2 dB > >Dave KH6AQ > > On Wed, Mar 11, 2020 at 1:49 AM Chris Moulding < > chr...@crosscountrywireless.net> wrote: > >> As well as being a radio amateur (G4HYG) I also run a small business >> designing and making radio equipment (Cross Country Wireless). >> >> Recently I've been asked by a radio contest group to see if I can >> redesign the YCCC Hi Z amplifier using modern components and using >> similar mounting arrangements to our Loop Antenna Amplifier. >> >> The first prototype using surface mount components is working well. >> >> So far I've not build an array of antennas but that will come later when >> the production boards arrive. >> >> The prototype uses a unity voltage gain amplifier and a BNC connector. >> >> I've a couple of questions for others on the list with experience of >> running vertical receive arrays: >> >> Is a unity voltage gain amplifier OK or do you think it needs more gain >> for long coax runs? >> >> At present I'm using a BNC male connector for the output. Would an F >> type connector be more compatible with existing antenna arrays. >> >> 73, Chris G4HYG >> >> _ >> Searchable Archives: http://www.contesting.com/_topband - Topband >> Reflector >> > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Lankford's stuff works great. I have used his antenna which does NOT use a preamp.it's only suitable for situations where match to the feedline isn't critical, but it sure is great to not have any preamp outside. de K8RYU From: Topband on behalf of Mikek Sent: Thursday, March 12, 2020 7:29 PM To: topband@contesting.com Subject: Topband: Hi Z amplifiers for 160m I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'. He designed it for phased loop antennas for the MW band. I believe it will work to at least to 9 MHz and maybe to 30 MHz. The specs High input Z, ~100 ohm output Z. He lists input intercepts: IIP2 = ~ +88dbm and IIP3 = ~+41dbm in the MW band. The webpage has some noise measurements on pages 3, 4, and 5 that were over my head. This page has more than just his amp but enough so you can understand it. If anyone has an interest, I have some more files in my computer. > https://www.okdxf.eu/lankford/Hi%20Z%20PPL%20Loop%20And%20Flag%20Arrays.pdf I have a plan to put a matching transformer and a Hi Z amp on my antenna with relay switching, so I can do a real A, B, comparison. If you have any advice on implementing that or advice about common mode filtering, I'm listening. Better relay suggestions would be appreciated. Mikek KF4ITA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m (LONG)
To assess the impact of amplifier circuit noise in "active" receive arrays, we only need to be concerned with the contribution of amplifier circuit noise relative to atmospheric noise. The details of how signals are phased in any particular array do not matter. The objective is to keep the total contribution of amplifier noise far below the atmospheric noise so as not to degrade the overall system noise floor in any significant way. However, we need to understand that the combiner circuit that phases up the signals in a receive phased array responds very differently to amplifier noise and atmospheric noise. This makes it less obvious how to determine whether the circuit noise of a particular amplifier is "low enough". Fortunately, there is a simple way to determine that using basic principles. Let's start with a single amplified vertical antenna. To simplify the analysis, we just set the gain of the vertical to 0 dB. In practice we can do a NEC analysis to calculate absolute gain in dBi, factoring in real losses but that is not necessary and does not change the conclusions. The antenna feedpoint amplifier adds its own noise to whatever signal plus atmospheric noise is received by the vertical. Let's set the circuit noise power equal to one "circuit noise unit" and the atmospheric noise power to one "atmospheric noise unit". Of course we can put voltage (or power) numbers on those units, based on properties of the amplifier, the atmospheric noise, the actual antenna gain, and the measurement bandwidth. However, that makes things unnecessarily complicated, so we won't do that. Next we create an array of N amplified vertical antennas, each one identical to the single vertical we started out with. We feed the signals from all the antenna amplifiers into an ideal combiner circuit that does not add its own noise. The combiner circuit phases up signals to create a directive beam pattern. Now we ask how much atmospheric noise appears in the phased up sum compared to the amount of total amplifier circuit noise. The atmospheric noises received at the various verticals are all correlated. The correlation comes about because the atmospheric noise is the same at each vertical except for time delay differences caused by geometric path length differences to each antenna element. However, as I described in an earlier e-mail, the amplifier circuit noises coming from each of the antenna amplifiers are all uncorrelated. For uncorrelated noises, the combiner simply adds the circuit noise powers of the individual amplifiers as I described previously. For N elements with N amplifiers, the total circuit noise power out of the combiner is then N times one "circuit noise unit" (ignoring any additional gain or throughput loss imparted by the combiner circuit). To determine the total atmospheric noise coming out of the combiner circuit, let's assume the atmospheric noise has a completely uniform distribution in 3-dimensional space. That is, the strength of the atmospheric noise is the same in every direction. This is an idealized assumption, but is often a reasonable approximation to reality. Under these assumptions, the total atmospheric noise out of the combiner turns out to be just one "atmospheric noise unit"! In other words, it is exactly the same as the atmospheric noise coming out of a single vertical. This is because the total atmospheric noise power picked up by the array is just the gain of the array (relative to a single vertical) averaged over all of 3-dimensional space times one "atmospheric noise unit" (the noise picked up by a single vertical). That average gain is exactly 0 dB, so the total atmospheric noise doesn't change in our idealized system. It doesn't matter what the antenna pattern is; the average gain is always 0 dB, which is why we did not need to be concerned with details of how signals are phased up to form a beam pattern. Of course, a different gain applies to actual signals that are coming from a specific direction and are not uniformly distributed like atmospheric noise, which is why we see a S/N improvement when the array is aimed at a signal of interest. So, we have demonstrated that in relative terms, the amplifier circuit noise power in an array of N amplified antennas goes up by a factor N whereas the atmospheric noise does not change. That increase in the amplifier noise contribution relative to atmospheric noise degrades the overall noise figure of the system. However, as long as we keep the amplifier noise contribution small enough, the noise figure degradation can also be kept to a minimum. That is why having more amplified elements makes it more important to design the antenna amplifiers for low circuit noise. 73, John W1FV -Original Message- From: Topband [mailto:topband-bounces+john.kaufmann=verizon@contesting.com] On Behalf Of Michael Tope Sent: Thursday, March
Re: Topband: Hi Z amplifiers for 160m
On 3/12/2020 4:13 AM, John Kaufmann via Topband wrote: I think you are confusing voltage and power. For incoherent sources like amplifier noise, the voltages of multiple incoherent sources add in a root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent sources is square root of eight times a single noise source, assuming equal combining ratios. However, because power is proportional to the square of voltage, then the*power* of the combined sum is the sum of the individual noise powers. As long as they are measured at the same point in any given circuit, dB computations for power and for voltage yield the same result provided that the nature of the signals, their frequencies, and phase relationships are taken into account. It's important to remember that the fundamental definition of dB is the log of a POWER ratio; it gets tied to voltage when circuit impedance is defined. And that PHASE has meaning only at a single frequency. The above computations can get messy when impedances vary with frequency, and as the phase relationship between coherent signals vary with frequency, position, and time offsets. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
There are a lot of SMT to DIP adapter boards out there which would allow newer SMD op-amps to be used in older through-hole PWB layouts. https://www.digikey.com/product-detail/en/aries-electronics/LCQT-SOIC8-8/A880AR-ND/4754588 73, Mike W4EF. On 3/12/2020 1:15 PM, Lee STRAHAN wrote: John, Yes of course you are quite correct. I stand corrected. I should not have used the word power. My thinking was along the line of what Mike W4EF posted. Just did not say it right. Also, I have never disagreed with your choice of the 8055 as I was aware of why you made that decision. Fortunately for us there are some op-amps now that show some really great specs. Unfortunately for us a lot of the older through the hole mount parts are disappearing quickly. Surface mount seems here to stay. Lee K7TJR From: John Kaufmann Sent: Thursday, March 12, 2020 4:14 AM To: k7...@msn.com; topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m Lee, I think you are confusing voltage and power. For incoherent sources like amplifier noise, the voltages of multiple incoherent sources add in a root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent sources is square root of eight times a single noise source, assuming equal combining ratios. However, because power is proportional to the square of voltage, then the *power* of the combined sum is the sum of the individual noise powers. This is well known in the theory of random processes, which is the basis of communications theory. So, what I said earlier is correct. For a system with eight amplifiers, the effective total noise power in the sum is eight times the individual noise powers when the sources are combined with equal weights. The YCCC array does not use equal weights, so the powers have be weighted when combining them to get the total noise power. 73, John W1FV -Original Message- From: Lee STRAHAN mailto:k7...@msn.com>> To: topband@contesting.com<mailto:topband@contesting.com> mailto:topband@contesting.com>> Sent: Wed, Mar 11, 2020 10:22 pm Subject: Re: Topband: Hi Z amplifiers for 160m Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S
Re: Topband: Hi Z amplifiers for 160m
Hi Lee, Yes, if you are combining coherent signals that are not in phase, then the each of the voltage vectors is weighted by cos(phi-i) where phi-i is the angle between the i-th voltage vector and the 1st vector. If phi=0, then you have the case I described previously. I can see how this can get tricky, however, with an electrically short baseline where you are striving for cancellation in the rearward looking direction. It's like you cancel in the rearward direction and almost cancel in the preferred direction :-). This degrades the SNR not because the noise is adding up, but because the signals are subtracting down. 73, Mike W4EF. On 3/11/2020 10:23 PM, Lee STRAHAN wrote: Mike and all, Well stated Mike. It's been a long time since we have conversed. The modifier to this is when the signals coming into the combiner are no longer in phase or coherent. This as a result of delay lines and time of signal arrival at the many elements. Most often in our small portion of a wavelength low frequency arrays the combination of signals is subtractive to form a given pattern per array dimension. This then lowers the signal to noise ratio. It gets pretty complicated to arrive at a noise figure. The only way we have been able to do this with amplified arrays is to simulate the array in NEC being excited with a known signal many wavelengths away. We can extract the actual amplitude and phase of these multi element array signals and then combine them mathematically as you have done by example to arrive at a signal gain number from signal combination. The noise gain is easy. I say we because I have a retired very smart Ham friend in Finland that has helped me through this. I t h as caused me to rethink gain distribution in some of my arrays. Lee K7TJR OR What matters is the signal-to-noise ratio (SNR). Take the canonical example of an ideal 2-port Wilkinson power combiner with in-phase coherent signals of 10 Vrms applied to each input along with 1 Vrms random thermal noise from the respective element amplifiers applied to each input (i.e. each input signal has a 20*log(10 Vrms/1 Vrms) = 20dB SNR). The power loss of the combiner is 3.01 dB [i.e. 10*log(2)], so voltage of each signal is attenuated by 1/sqrt(2) = 0.707. Thus, the components of each input signal appearing at the output are 7.07 Vrms each and 0.707 for each of the noise inputs. The signal components add coherently at the combiner output yielding a total signal voltage of 14.14 Volts rms. The noise voltages are incoherent, so they add as root-sum-square at the output of the combiner. This yields a total noise voltage of sqrt(0.707^2 + 0.707^2) = sqrt(1) = 1.0 Vrms. Thus, the combined noise voltage is unchanged, but the signal voltage goes up by sqrt(2). The SNR of the combined output = 20*log(14.14Vrms/1Vrms) = 23dB, a 3dB improvement. The same things holds for an ideal N-way combiner with equals noise components at each input. The noise power at the combined output equals the noise power of any of the equal input components (i.e. 0dB gain). 73, Mike W4EF.. On 3/11/2020 7:22 PM, Lee STRAHAN wrote: Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design
Re: Topband: Hi Z amplifiers for 160m
John, Yes of course you are quite correct. I stand corrected. I should not have used the word power. My thinking was along the line of what Mike W4EF posted. Just did not say it right. Also, I have never disagreed with your choice of the 8055 as I was aware of why you made that decision. Fortunately for us there are some op-amps now that show some really great specs. Unfortunately for us a lot of the older through the hole mount parts are disappearing quickly. Surface mount seems here to stay. Lee K7TJR From: John Kaufmann Sent: Thursday, March 12, 2020 4:14 AM To: k7...@msn.com; topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m Lee, I think you are confusing voltage and power. For incoherent sources like amplifier noise, the voltages of multiple incoherent sources add in a root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent sources is square root of eight times a single noise source, assuming equal combining ratios. However, because power is proportional to the square of voltage, then the *power* of the combined sum is the sum of the individual noise powers. This is well known in the theory of random processes, which is the basis of communications theory. So, what I said earlier is correct. For a system with eight amplifiers, the effective total noise power in the sum is eight times the individual noise powers when the sources are combined with equal weights. The YCCC array does not use equal weights, so the powers have be weighted when combining them to get the total noise power. 73, John W1FV -Original Message- From: Lee STRAHAN mailto:k7...@msn.com>> To: topband@contesting.com<mailto:topband@contesting.com> mailto:topband@contesting.com>> Sent: Wed, Mar 11, 2020 10:22 pm Subject: Re: Topband: Hi Z amplifiers for 160m Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S. This gives the best overall linear dynamic range with a preamplified short vertical system. There is no loss in noise performance because the noise on 160 and 80 is totally dominated by atmospheric noise. In measurements I made at my QTH, the internal noise of the YCCC preamp is about 10 dB lower than my d
Re: Topband: Hi Z amplifiers for 160m
Chris, Good choice. Perhaps one note of caution. With a BJT input like this the input current noise may be more dominant, unless the input impedance is kept low. Would be great to see the final design. GL and 73, George, AA7JV On Thu, 12 Mar 2020 10:10:44 + Chris Moulding wrote: Thanks again for all the comments. Very interesting especially the reasoning behind the designs. The device I've picked for my design is the LTC6228. This is a new device by Analog Devices that only came out late last year. The voltage noise is 0.88 uV/sqrt Hz and the current noise is 3 pA/sqrt Hz. Claimed output IP product performance is <-100 dBc at 4V peak to peak output. The device is available in SOT-23 package from DigiKey and Mouser. I'm planning to use the imminent coronavirus lockdown over here in the UK to get some PCB designs done. 73, Chris G4HYG _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
*JFET op amp vs bipolar op amps, *LTSpice simulations connected to a 3 meter monopole A bipolar op amp doesn't always give the lowest noise with a short monopole at 1.8 MHz because the op amp current noise creates noise voltage across the antenna capacitive reactance. Additonally, op amps can be connected in parallel for lower voltage noise at the expense of higher input capacitance (which loads down the antenna signal voltage). Simulations of the YCCC amp with a bipolar op amp and a JFET op amp were performed. Next, preamps having 2, 4 and 6 JFET op amps were modeled. As the number of op amps goes up the antenna voltage goes down with optimum S/N ratio, in this case, with 4 op amps. It shows 4.5 dB better S/N than the bipolar op amp. The bipolar op circuit is modeled with an LTC6228 rather than an AD8045 because I didn't have to import the AD8045 model into LTSpice. I can try to import the AD8045 later if anyone is interested. The LTC6228 op amp has 1/3 the voltage noise and the same current noise with Bias Current Compensation disabled, so it should show lower noise than the AD8045. The JFET op amp is the ADA4637 and IMD simulations were run with it looking better than the bipolar. *YCCC amp with bipolar vs JFET op amp for a 3 meter monopole at 1.8 MHz* LTC6228 bipolar op amp, 9.5 nV/Hz^0.5, loaded sig 0.93, relative S/N ratio 0 dB ADA4637 JFET op amp, 6.7 nV/Hz^0.5, loaded sig 0.85, relative S/N ratio 2.2 dB 2 X JFET op amp, 4.8 nV/Hz^0.5, loaded sig 0.74, relative S/N ratio 3.9 dB 4 X JFET op amp, 3.6 nV/Hz^0.5, loaded sig 0.59, relative S/N ratio *4.5 dB* 6 X JFET op amp, 3.1 nV/Hz^0.5, loaded sig 0.49, relative S/N ratio 4.2 dB Dave KH6AQ On Wed, Mar 11, 2020 at 1:49 AM Chris Moulding < chr...@crosscountrywireless.net> wrote: > As well as being a radio amateur (G4HYG) I also run a small business > designing and making radio equipment (Cross Country Wireless). > > Recently I've been asked by a radio contest group to see if I can > redesign the YCCC Hi Z amplifier using modern components and using > similar mounting arrangements to our Loop Antenna Amplifier. > > The first prototype using surface mount components is working well. > > So far I've not build an array of antennas but that will come later when > the production boards arrive. > > The prototype uses a unity voltage gain amplifier and a BNC connector. > > I've a couple of questions for others on the list with experience of > running vertical receive arrays: > > Is a unity voltage gain amplifier OK or do you think it needs more gain > for long coax runs? > > At present I'm using a BNC male connector for the output. Would an F > type connector be more compatible with existing antenna arrays. > > 73, Chris G4HYG > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Lee, I think you are confusing voltage and power. For incoherent sources like amplifier noise, the voltages of multiple incoherent sources add in a root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent sources is square root of eight times a single noise source, assuming equal combining ratios. However, because power is proportional to the square of voltage, then the *power* of the combined sum is the sum of the individual noise powers. This is well known in the theory of random processes, which is the basis of communications theory. So, what I said earlier is correct. For a system with eight amplifiers, the effective total noise power in the sum is eight times the individual noise powers when the sources are combined with equal weights. The YCCC array does not use equal weights, so the powers have be weighted when combining them to get the total noise power. 73, John W1FV -Original Message- From: Lee STRAHAN To: topband@contesting.com Sent: Wed, Mar 11, 2020 10:22 pm Subject: Re: Topband: Hi Z amplifiers for 160m Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S. This gives the best overall linear dynamic range with a preamplified short vertical system. There is no loss in noise performance because the noise on 160 and 80 is totally dominated by atmospheric noise. In measurements I made at my QTH, the internal noise of the YCCC preamp is about 10 dB lower than my daytime atmospheric noise on 160m when using a vertical about 20 feet high. You must also consider the number of active elements in an amplified antenna array when evaluating overall system noise performance. This is because the amplifier circuit noise power of all the feedpoint amplifiers is added together when the elements are phased up in a combiner. If you have N elements in your array, the effective circuit noise contribution gets multiplied by N. The YCCC array has 3 active elements at a time. However, the YCCC design is somewhat unusual in that maximum RDF is achieved when the signals from the elements are combined in unequal ratios. As a result the effective amplifier circuit noise contribution is less than 3 times (or 4.8 dB) the noise o
Re: Topband: Hi Z amplifiers for 160m
Thanks again for all the comments. Very interesting especially the reasoning behind the designs. The device I've picked for my design is the LTC6228. This is a new device by Analog Devices that only came out late last year. The voltage noise is 0.88 uV/sqrt Hz and the current noise is 3 pA/sqrt Hz. Claimed output IP product performance is <-100 dBc at 4V peak to peak output. The device is available in SOT-23 package from DigiKey and Mouser. I'm planning to use the imminent coronavirus lockdown over here in the UK to get some PCB designs done. 73, Chris G4HYG _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Mike and all, Well stated Mike. It's been a long time since we have conversed. The modifier to this is when the signals coming into the combiner are no longer in phase or coherent. This as a result of delay lines and time of signal arrival at the many elements. Most often in our small portion of a wavelength low frequency arrays the combination of signals is subtractive to form a given pattern per array dimension. This then lowers the signal to noise ratio. It gets pretty complicated to arrive at a noise figure. The only way we have been able to do this with amplified arrays is to simulate the array in NEC being excited with a known signal many wavelengths away. We can extract the actual amplitude and phase of these multi element array signals and then combine them mathematically as you have done by example to arrive at a signal gain number from signal combination. The noise gain is easy. I say we because I have a retired very smart Ham friend in Finland that has helped me through this. It h as caused me to rethink gain distribution in some of my arrays. Lee K7TJR OR What matters is the signal-to-noise ratio (SNR). Take the canonical example of an ideal 2-port Wilkinson power combiner with in-phase coherent signals of 10 Vrms applied to each input along with 1 Vrms random thermal noise from the respective element amplifiers applied to each input (i.e. each input signal has a 20*log(10 Vrms/1 Vrms) = 20dB SNR). The power loss of the combiner is 3.01 dB [i.e. 10*log(2)], so voltage of each signal is attenuated by 1/sqrt(2) = 0.707. Thus, the components of each input signal appearing at the output are 7.07 Vrms each and 0.707 for each of the noise inputs. The signal components add coherently at the combiner output yielding a total signal voltage of 14.14 Volts rms. The noise voltages are incoherent, so they add as root-sum-square at the output of the combiner. This yields a total noise voltage of sqrt(0.707^2 + 0.707^2) = sqrt(1) = 1.0 Vrms. Thus, the combined noise voltage is unchanged, but the signal voltage goes up by sqrt(2). The SNR of the combined output = 20*log(14.14Vrms/1Vrms) = 23dB, a 3dB improvement. The same things holds for an ideal N-way combiner with equals noise components at each input. The noise power at the combined output equals the noise power of any of the equal input components (i.e. 0dB gain). 73, Mike W4EF.. On 3/11/2020 7:22 PM, Lee STRAHAN wrote: > Hello John and all, > Concerning the adding the noise in a typical array. If the noise was > coherent or exactly the same signal from each element/amp the summed noise > would indeed be 8 times. However circuit noise is always random and > incoherent which causes the summation to be a single noise power times the > square root of the number of elements assuming equal levels from each amp. In > the case of 8 elements 4.5 dB increase which is no small matter as well. In > the case of the three elements the noise summation would be about 2.4 dB > higher than a single element. > Lee K7TJR OR > > As the designer of the YCCC high impedance feedpoint amplifier, let me > address some issues related to the design of the YCCC amplifier as well as > feedpoint amplifiers in general. If you don't want to read a lot of > technical gobbledygook, please disregard this message. > > The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points > out, there are most certainly better op amps out there. However, the AD8055 > was the "best" part I could find in a DIP-8 package. The "better" op amps > are all SMT parts but given that the YCCC preamp was a kit, I intentionally > limited the selection to DIP-8 parts that kit builders could work with > relatively easily on a PCB. Not everyone is able to do a competent job > soldering tiny SMT parts. > > Within the universe of available RF op amps, tradeoffs must be made in terms > of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part > but it has excellent linearity and plenty of bandwidth for HF use. At my QTH > there is an AM BCB station 3 miles away, which makes it a somewhat > challenging EMI environment. The decision to run the op amp in a unity gain > configuration comes down to linear dynamic range. It is easy to design for > more gain, but it is also easily demonstrated that you will begin to suffer > in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero > BCB intermods or distortion products in the 160m band at my QTH. > > In general I do not like to use an outboard preamplifier between the > output of the phased array combiner circuit and my receiver because it > degrades the linear dynamic range of the system. The YCCC system > user's manual (Section > 12.1) does specify several outboard preamps that could be used. In a low EMI > environment, I think they all work fine. However, at my QTH, with the nearby > AM BCB station, all of
Re: Topband: Hi Z amplifiers for 160m
On 3/11/2020 9:39 PM, Michael Tope wrote: The signal components add coherently at the combiner output yielding a total signal voltage of 14.14 Volts rms. The noise voltages are incoherent, so they add as root-sum-square at the output of the combiner. This yields a total noise voltage of sqrt(0.707^2 + 0.707^2) = sqrt(1) = 1.0 Vrms. Thus, the combined noise voltage is unchanged, but the signal voltage goes up by sqrt(2). This is also why averaging in measurement systems and spectral displays improves their signal to noise ratio. As the number of averages is increased, signal to noise increases using the same math as above. I set averaging on my P3 to the max, the noise averages out, adjust the display reference level so that the noise is at the bottom of the display, causing even the weakest carriers (or CW) to be seen above the noise (and as faint traces in the waterfall). We used averaging extensively in pro audio measurement systems, beginning with Time Delay Spectrometry around 1982. Which, by the way, was invented about ten years earlier by the late Richard Heyser, was was at JPL at the time. In this AES Paper, I buried a TDS sweep in a music track at a level that was nearly inaudible and fed it through a popular broadcast audio processor to study it's dynamic frequency response at high levels of compression. The sweep was nearly inaudible, the the system was able to recover it by 64X averaging, combined with TDS's inherent noise rejection. http://k9yc.com/AESPaper-TDS.pdf 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
What matters is the signal-to-noise ratio (SNR). Take the canonical example of an ideal 2-port Wilkinson power combiner with in-phase coherent signals of 10 Vrms applied to each input along with 1 Vrms random thermal noise from the respective element amplifiers applied to each input (i.e. each input signal has a 20*log(10 Vrms/1 Vrms) = 20dB SNR). The power loss of the combiner is 3.01 dB [i.e. 10*log(2)], so voltage of each signal is attenuated by 1/sqrt(2) = 0.707. Thus, the components of each input signal appearing at the output are 7.07 Vrms each and 0.707 for each of the noise inputs. The signal components add coherently at the combiner output yielding a total signal voltage of 14.14 Volts rms. The noise voltages are incoherent, so they add as root-sum-square at the output of the combiner. This yields a total noise voltage of sqrt(0.707^2 + 0.707^2) = sqrt(1) = 1.0 Vrms. Thus, the combined noise voltage is unchanged, but the signal voltage goes up by sqrt(2). The SNR of the combined output = 20*log(14.14Vrms/1Vrms) = 23dB, a 3dB improvement. The same things holds for an ideal N-way combiner with equals noise components at each input. The noise power at the combined output equals the noise power of any of the equal input components (i.e. 0dB gain). 73, Mike W4EF.. On 3/11/2020 7:22 PM, Lee STRAHAN wrote: Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S. This gives the best overall linear dynamic range with a preamplified short vertical system. There is no loss in noise performance because the noise on 160 and 80 is totally dominated by atmospheric noise. In measurements I made at my QTH, the internal noise of the YCCC preamp is about 10 dB lower than my daytime atmospheric noise on 160m when using a vertical about 20 feet high. You must also consider the number of active elements in an amplified antenna array when evaluating overall system noise performance. This is because the amplifier circuit noise power of all the feedpoint amplifiers is added together when the elements are phased up in a combiner. If you have N elements in your array, the effective circuit noise contribution gets multiplied by N. The YCCC array has 3 active
Re: Topband: Hi Z amplifiers for 160m
Here is an example at Digikey: ACX1545-ND Expensive, but... 73, George On Wed, 11 Mar 2020 13:33:08 -0400 DXer wrote: >>>Use an F connector (a high quality one that can be torqued.) Can you point to a place that sells them. I became a 'fan' of F termination, but have recently had second thoughts because of the bulkhead connector's quality. Thanks and 73. Vince, VA3VF _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Hello John and all, Concerning the adding the noise in a typical array. If the noise was coherent or exactly the same signal from each element/amp the summed noise would indeed be 8 times. However circuit noise is always random and incoherent which causes the summation to be a single noise power times the square root of the number of elements assuming equal levels from each amp. In the case of 8 elements 4.5 dB increase which is no small matter as well. In the case of the three elements the noise summation would be about 2.4 dB higher than a single element. Lee K7TJR OR As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S. This gives the best overall linear dynamic range with a preamplified short vertical system. There is no loss in noise performance because the noise on 160 and 80 is totally dominated by atmospheric noise. In measurements I made at my QTH, the internal noise of the YCCC preamp is about 10 dB lower than my daytime atmospheric noise on 160m when using a vertical about 20 feet high. You must also consider the number of active elements in an amplified antenna array when evaluating overall system noise performance. This is because the amplifier circuit noise power of all the feedpoint amplifiers is added together when the elements are phased up in a combiner. If you have N elements in your array, the effective circuit noise contribution gets multiplied by N. The YCCC array has 3 active elements at a time. However, the YCCC design is somewhat unusual in that maximum RDF is achieved when the signals from the elements are combined in unequal ratios. As a result the effective amplifier circuit noise contribution is less than 3 times (or 4.8 dB) the noise of a single amplifier. In fact because of the unequal combining ratios, the actual effective noise goes up by a bit less than 2 dB compared to a single amplifier. An array like the Hi-Z array with 8 active elements combines the elements in equal proportion so the effective amplifier circuit noise of the system is 8 times (or 9 dB) higher than the noise of a single amplifier. For this reason, the YCCC array can tolerate noisier amplifiers without degrading system noise performance. The objective is to keep circuit noise well under atmospheric noise. On the subject of op amp noise specs, you must consider *both* input voltage noise and input current noise because, in general, both contribute to the total output amplifier noise. It is not good enough to pick an op amp with low input voltage noise without also considering the input current noise. For a good noise analysis, download a copy of the datasheet for the CLC425 op amp: http://www.elektronikjk.pl/elementy_czynne/IC/CLC425.pdf. Refer to pages 8-10. (The CLC425 is a very good RF op amp but has been obsoleted by
Re: Topband: Hi Z amplifiers for 160m
As the designer of the YCCC high impedance feedpoint amplifier, let me address some issues related to the design of the YCCC amplifier as well as feedpoint amplifiers in general. If you don't want to read a lot of technical gobbledygook, please disregard this message. The YCCC uses an AD8055 RF amp as the gain element. As Lee, K7TJF, points out, there are most certainly better op amps out there. However, the AD8055 was the "best" part I could find in a DIP-8 package. The "better" op amps are all SMT parts but given that the YCCC preamp was a kit, I intentionally limited the selection to DIP-8 parts that kit builders could work with relatively easily on a PCB. Not everyone is able to do a competent job soldering tiny SMT parts. Within the universe of available RF op amps, tradeoffs must be made in terms of noise, linearity, and bandwidth. The AD8055 is not the lowest noise part but it has excellent linearity and plenty of bandwidth for HF use. At my QTH there is an AM BCB station 3 miles away, which makes it a somewhat challenging EMI environment. The decision to run the op amp in a unity gain configuration comes down to linear dynamic range. It is easy to design for more gain, but it is also easily demonstrated that you will begin to suffer in terms of unwanted intermods. With the YCCC preamp, I get absolutely zero BCB intermods or distortion products in the 160m band at my QTH. In general I do not like to use an outboard preamplifier between the output of the phased array combiner circuit and my receiver because it degrades the linear dynamic range of the system. The YCCC system user's manual (Section 12.1) does specify several outboard preamps that could be used. In a low EMI environment, I think they all work fine. However, at my QTH, with the nearby AM BCB station, all of them, without exception, generate increased distortion and intermod, which I find unacceptable. It is always desirable to apply RF gain with a roofing filter in front, which is becoming common practice in high performance receivers. With my K3S receiver, the use of a unity gain antenna feedpoint preamplifier is perfectly fine if you also turn on the preamp in the K3S. This gives the best overall linear dynamic range with a preamplified short vertical system. There is no loss in noise performance because the noise on 160 and 80 is totally dominated by atmospheric noise. In measurements I made at my QTH, the internal noise of the YCCC preamp is about 10 dB lower than my daytime atmospheric noise on 160m when using a vertical about 20 feet high. You must also consider the number of active elements in an amplified antenna array when evaluating overall system noise performance. This is because the amplifier circuit noise power of all the feedpoint amplifiers is added together when the elements are phased up in a combiner. If you have N elements in your array, the effective circuit noise contribution gets multiplied by N. The YCCC array has 3 active elements at a time. However, the YCCC design is somewhat unusual in that maximum RDF is achieved when the signals from the elements are combined in unequal ratios. As a result the effective amplifier circuit noise contribution is less than 3 times (or 4.8 dB) the noise of a single amplifier. In fact because of the unequal combining ratios, the actual effective noise goes up by a bit less than 2 dB compared to a single amplifier. An array like the Hi-Z array with 8 active elements combines the elements in equal proportion so the effective amplifier circuit noise of the system is 8 times (or 9 dB) higher than the noise of a single amplifier. For this reason, the YCCC array can tolerate noisier amplifiers without degrading system noise performance. The objective is to keep circuit noise well under atmospheric noise. On the subject of op amp noise specs, you must consider *both* input voltage noise and input current noise because, in general, both contribute to the total output amplifier noise. It is not good enough to pick an op amp with low input voltage noise without also considering the input current noise. For a good noise analysis, download a copy of the datasheet for the CLC425 op amp: http://www.elektronikjk.pl/elementy_czynne/IC/CLC425.pdf. Refer to pages 8-10. (The CLC425 is a very good RF op amp but has been obsoleted by newer parts). I put the noise equations into an Excel spreadsheet, which allowed me to compare many different op amps in terms of total noise performance, using their input current noise and voltage noise specs. Not all op amps publish specs on linearity. It is safe to assume that if no specs are given, the linearity is not particularly outstanding. Look for harmonic distortion (HD2 and HD3) as well as TOI (third-order intercept) data. You do have to be careful in interpreting the data because the linearity is directly tied to the amplifier gain configuration. If I were to recommend a particularly outstanding RF op amp, it would
Re: Topband: Hi Z amplifiers for 160m
Lee, Can you recommend an improved device to replace/upgrade the Analog Devices # AD8055AN chip? Any chance it would be a "drop-in replacement" ( pin-for-pin ) ? I've got nine of the YCCC that I'd like to upgrade. Or maybe I should just wait for Chris to complete his whole new design. 73 Lloyd - N9LB -Original Message- From: Topband [mailto:topband-bounces+lloydberg=tds@contesting.com] On Behalf Of Lee STRAHAN Sent: Wednesday, March 11, 2020 12:17 PM To: topband@contesting.com Subject: Re: Topband: Hi Z amplifiers for 160m Greetings all, George has some very pertinent points here and only on one point I will disagree. What a Hi-Z amplifier needs to do is dependent on your aspirations of the size and quantity of elements you decide to use. The combiner losses will dictate what you must do at the element end of an array for an amplifier. Let me clear one thing up. The YCCC amplifier is not a unity gain amplifier. It has a 6 dB loss due to its output impedance of around 75 ohms. Thus the evolution of what I called the +6 amps 6 or 7 years ago that indeed have unity gain and still have a 75 ohm output impedance. A significant reduction in the noise figure of an array with a lossy combiner. If ones aspirations are only to use a simple array like the YCCC then the operational amplifier versions seem to fill the bill, but don't expect then to apply the same amplifiers as you build arrays for higher and higher RDF. And, there are much better amplifiers available to replace the 8055 if I remember the YCCC part number correctly. The 8055 has like 4nV/root Hz noise while some of the new ones get down to 1 nV/root Hz noise a very significant improvement. I could bore you all to distraction with other fine points that Hi-Z amps need as specifications. It may not meet the eye but that is why performance comes at a price. Lee K7TJR Hi-Z Antennas Chris, Assuming a trans-impedance amplifier, "unity gain" is enough (with reasonable size elements). Noise and IP3 are far more important. Lightning and surge immunity are also important. Also, isolate the amp from common mode noise travelling on the feed-line. Filter the power supply well. Use an F connector (a high quality one that can be torqued.) GL and 73, George, AA7JV/C6AGU On Wed, 11 Mar 2020 11:33:34 + Chris Moulding wrote: > As well as being a radio amateur (G4HYG) I also run a small business designing and making radio equipment (Cross Country Wireless). > > Recently I've been asked by a radio contest group to see if I can redesign the YCCC Hi Z amplifier using modern components and using similar mounting arrangements to our Loop Antenna Amplifier. > > The first prototype using surface mount components is working well. > > So far I've not build an array of antennas but that will come later when the production boards arrive. > > The prototype uses a unity voltage gain amplifier and a BNC connector. > > I've a couple of questions for others on the list with experience of running vertical receive arrays: > > Is a unity voltage gain amplifier OK or do you think it needs more gain for long coax runs? > > At present I'm using a BNC male connector for the output. Would an F type connector be more compatible with existing antenna arrays. > > 73, Chris G4HYG > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Thanks for all the very helpful replies and suggestions. I'll change the BNC connector to a 4 hole F connector with 75 ohm output. The design already has a 20 kA gas discharge tube and DC biased diode limiter for lightning and surge protection. It also has an optional (by internal link) diode limiter on the output so that it can be used by "weak" SDR receivers such as the SDRPlay RSP series that cannot take high RF levels. I agree with the comment on adding a common mode choke on the coax output. The amplifier device I'm using has very low noise so it needs extra common mode isolation to allow use at very RF quiet locations. I'm planning to take a trip to the nearest beach this weekend to try the prototype in a very low noise location. 73, Chris G4HYG _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Mouser 601- 25-7630 or 601-25-7660 [Lee K7TJR] >>>Use an F connector (a high quality one that can be torqued.) Can you point to a place that sells them. I became a 'fan' of F termination, but have recently had second thoughts because of the bulkhead connector's quality. Thanks and 73. Vince, VA3VF _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
On 3/11/2020 6:28 AM, GEORGE WALLNER wrote: Assuming a trans-impedance amplifier, "unity gain" is enough (with reasonable size elements). Noise and IP3 are far more important. Lightning and surge immunity are also important. Also, isolate the amp from common mode noise travelling on the feed-line. Filter the power supply well. Use an F connector (a high quality one that can be torqued.) Agreed, but I would add power on the coax. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Greetings all, George has some very pertinent points here and only on one point I will disagree. What a Hi-Z amplifier needs to do is dependent on your aspirations of the size and quantity of elements you decide to use. The combiner losses will dictate what you must do at the element end of an array for an amplifier. Let me clear one thing up. The YCCC amplifier is not a unity gain amplifier. It has a 6 dB loss due to its output impedance of around 75 ohms. Thus the evolution of what I called the +6 amps 6 or 7 years ago that indeed have unity gain and still have a 75 ohm output impedance. A significant reduction in the noise figure of an array with a lossy combiner. If ones aspirations are only to use a simple array like the YCCC then the operational amplifier versions seem to fill the bill, but don't expect then to apply the same amplifiers as you build arrays for higher and higher RDF. And, there are much better amplifiers available to replace the 8055 if I remember the YCCC part number correctly. The 8055 has like 4nV/root Hz noise while some of the new ones get down to 1 nV/root Hz noise a very significant improvement. I could bore you all to distraction with other fine points that Hi-Z amps need as specifications. It may not meet the eye but that is why performance comes at a price. Lee K7TJR Hi-Z Antennas Chris, Assuming a trans-impedance amplifier, "unity gain" is enough (with reasonable size elements). Noise and IP3 are far more important. Lightning and surge immunity are also important. Also, isolate the amp from common mode noise travelling on the feed-line. Filter the power supply well. Use an F connector (a high quality one that can be torqued.) GL and 73, George, AA7JV/C6AGU On Wed, 11 Mar 2020 11:33:34 + Chris Moulding wrote: > As well as being a radio amateur (G4HYG) I also run a small business > designing and making radio equipment (Cross Country Wireless). > > Recently I've been asked by a radio contest group to see if I can redesign > the YCCC Hi Z amplifier using modern components and using similar mounting > arrangements to our Loop Antenna Amplifier. > > The first prototype using surface mount components is working well. > > So far I've not build an array of antennas but that will come later when the > production boards arrive. > > The prototype uses a unity voltage gain amplifier and a BNC connector. > > I've a couple of questions for others on the list with experience of running > vertical receive arrays: > > Is a unity voltage gain amplifier OK or do you think it needs more gain for > long coax runs? > > At present I'm using a BNC male connector for the output. Would an F type > connector be more compatible with existing antenna arrays. > > 73, Chris G4HYG > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Chris, I just finished making my own set of amplifiers derived from the YCCC design but using SMD components. I used an AD8045 (SOIC-8 size) instead of the 8055 and added a voltage regulator. They have replaced a set of the original Hi-Z amps (the ones in the black mini-boxes with metal covers) in my hexagonal array. I don't have a way to directly compare the performance of the new amps with the old ones, but so far they seem to work well. Tor N4OGW On Wednesday, March 11, 2020, 8:29:33 AM CDT, GEORGE WALLNER wrote: Chris, Assuming a trans-impedance amplifier, "unity gain" is enough (with reasonable size elements). Noise and IP3 are far more important. Lightning and surge immunity are also important. Also, isolate the amp from common mode noise travelling on the feed-line. Filter the power supply well. Use an F connector (a high quality one that can be torqued.) GL and 73, George, AA7JV/C6AGU On Wed, 11 Mar 2020 11:33:34 + Chris Moulding wrote: > As well as being a radio amateur (G4HYG) I also run a small business > designing and making radio equipment (Cross Country Wireless). > > Recently I've been asked by a radio contest group to see if I can redesign > the YCCC Hi Z amplifier using modern components and using similar mounting > arrangements to our Loop Antenna Amplifier. > > The first prototype using surface mount components is working well. > > So far I've not build an array of antennas but that will come later when the > production boards arrive. > > The prototype uses a unity voltage gain amplifier and a BNC connector. > > I've a couple of questions for others on the list with experience of running > vertical receive arrays: > > Is a unity voltage gain amplifier OK or do you think it needs more gain for > long coax runs? > > At present I'm using a BNC male connector for the output. Would an F type > connector be more compatible with existing antenna arrays. > > 73, Chris G4HYG > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Hi Z amplifiers for 160m
Chris, Assuming a trans-impedance amplifier, "unity gain" is enough (with reasonable size elements). Noise and IP3 are far more important. Lightning and surge immunity are also important. Also, isolate the amp from common mode noise travelling on the feed-line. Filter the power supply well. Use an F connector (a high quality one that can be torqued.) GL and 73, George, AA7JV/C6AGU On Wed, 11 Mar 2020 11:33:34 + Chris Moulding wrote: As well as being a radio amateur (G4HYG) I also run a small business designing and making radio equipment (Cross Country Wireless). Recently I've been asked by a radio contest group to see if I can redesign the YCCC Hi Z amplifier using modern components and using similar mounting arrangements to our Loop Antenna Amplifier. The first prototype using surface mount components is working well. So far I've not build an array of antennas but that will come later when the production boards arrive. The prototype uses a unity voltage gain amplifier and a BNC connector. I've a couple of questions for others on the list with experience of running vertical receive arrays: Is a unity voltage gain amplifier OK or do you think it needs more gain for long coax runs? At present I'm using a BNC male connector for the output. Would an F type connector be more compatible with existing antenna arrays. 73, Chris G4HYG _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
