Topband: BCB interference ?
Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Ed, I have the same problem. A 25KW station at 1560 KHz just destroys the front end of my K3. Elecraft did not do a vey good job on their front end filtering but that's another issue. I finally had to build a 7 pole HPF from W3NQN's article many years ago. The catch is it has to be able to handle the transmit power too. There is no room in the K3 for a receive filter. Elecraft just blew me off when I told them about the problem. They said I was 1 in a 1000 that had that problem and they were not going to fix it. You will need at least 40 dB of attenuation and to my knowledge none of the commercially available filters will do the job. I heard that Array Solutions might have a transmit HPF now but I have not looked into it. 73 Hardy N7RT - Original Message - From: Ed Stallman n...@airmail.net To: TopBand List topband@contesting.com Sent: Monday, September 22, 2014 6:50 AM Subject: Topband: BCB interference ? Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Orbital Angular Momentum propagation
Is anyone on list involved in any academic or commercial research on this topic ? If so can you contact me directly - w...@aol.com. Sent from my iPhone _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Hi Ed! I've got a 1650 KHz 10 KW station about six miles away. I am using a Clifton Laboratories Z10022A high pass filter for 160 meter reception. Works great and very reasonable price. http://www.cliftonlaboratories.com/current_products.htm Z10022A Medium Wave High Pass Filter The Z10022A is a receive-only 9th order 1 dB Chebyshev high pass filter with a nominal cutoff frequency of 1800 KHz. The Z10022A is intended to be used to prevent a shortwave receiver from overloading due to strong signals from AM broadcast band (Medium Wave) in the 530-1700 KHz range. ( see the web site for lots of documentation). http://www.cliftonlaboratories.com/z10022a_high_pass_filter.htm 73 Lloyd - N9LB On Mon, Sep 22, 2014 at 8:50 AM, Ed Stallman wrote: Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Hi Ed! I've got a 1650 KHz 10 KW station about six miles away. I am using a Clifton Laboratories Z10022A high pass filter for 160 meter reception. Works great and very reasonable price. http://www.cliftonlaboratories.com/current_products.htm Z10022A Medium Wave High Pass Filter The Z10022A is a receive-only 9th order 1 dB Chebyshev high pass filter with a nominal cutoff frequency of 1800 KHz. The Z10022A is intended to be used to prevent a shortwave receiver from overloading due to strong signals from AM broadcast band (Medium Wave) in the 530-1700 KHz range. ( see the web site for lots of documentation). http://www.cliftonlaboratories.com/z10022a_high_pass_filter.htm 73 Lloyd - N9LB On Mon, Sep 22, 2014 at 8:50 AM, Ed Stallman wrote: Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Why can't you come out of Ant out jack through filter and back in through ant in jack and select RX antenna? Stan, K5GO Sent from Stan's IPhone On Sep 22, 2014, at 8:07 AM, Hardy Landskov n...@cox.net wrote: Ed, I have the same problem. A 25KW station at 1560 KHz just destroys the front end of my K3. Elecraft did not do a vey good job on their front end filtering but that's another issue. I finally had to build a 7 pole HPF from W3NQN's article many years ago. The catch is it has to be able to handle the transmit power too. There is no room in the K3 for a receive filter. Elecraft just blew me off when I told them about the problem. They said I was 1 in a 1000 that had that problem and they were not going to fix it. You will need at least 40 dB of attenuation and to my knowledge none of the commercially available filters will do the job. I heard that Array Solutions might have a transmit HPF now but I have not looked into it. 73 Hardy N7RT - Original Message - From: Ed Stallman n...@airmail.net To: TopBand List topband@contesting.com Sent: Monday, September 22, 2014 6:50 AM Subject: Topband: BCB interference ? Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
On Mon,9/22/2014 7:07 AM, Hardy Landskov wrote: The catch is it has to be able to handle the transmit power too. Not if you put the filter in the RX loop. That feature is part of the KXV3 and KXV3A modules. Also, many AM broadcast stations are licensed for a lot less power at night than during the day. Check the FCC website for the station you're concerned about. Of course, that won't help at greyline. :) http://www.fcc.gov/encyclopedia/am-query-broadcast-station-search 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Matching network info for 80 160M needed
I have an Inverted-L antenna for 80M 160M and would like to make or buy a remote matching system that would work on both ends of both bands that would accept full power. I built a system many years ago from a Doug DeMaw, W1FB, article in the May 1985 issue of QST but it has never worked as well as I wanted for whatever reason. If anyone is interested, this article can be found at the ARRL QST archives http://www.arrl.org/arrl-periodicals-archive-search by entering W1FB , 1985, May, QST. Anyone have an idea of a matching system that would do all of the above ? _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Bill, The HPF article was in QST, Feb 1978, p. 22. Hardy - Original Message - From: Bill Wichers bi...@waveform.net To: Hardy Landskov n...@cox.net Sent: Monday, September 22, 2014 8:57 AM Subject: RE: Topband: BCB interference ? Do you have a link to that W3NQN article? I'm only familiar with his work with bandpass filters, and I'm looking for a good highpass filter design to use ahead of a receiving preamp myself. BTW, if you have the K3 with the KXV3A you can loop the receive signal out through an external device and back into the radio through a pair of BNC jacks (this is how you use their 6m preamp, for example). You could use that option to allow the use of external receive filters too. Just a thought... -Bill KB8WYP _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
See also http://www.arraysolutions.com/Products/bcb_filters_top.htm and http://arraysolutions.com/Products/bcb_filters_top1.htm . 73, Jim N7US -Original Message- Ed, I have the same problem. A 25KW station at 1560 KHz just destroys the front end of my K3. Elecraft did not do a vey good job on their front end filtering but that's another issue. I finally had to build a 7 pole HPF from W3NQN's article many years ago. The catch is it has to be able to handle the transmit power too. There is no room in the K3 for a receive filter. Elecraft just blew me off when I told them about the problem. They said I was 1 in a 1000 that had that problem and they were not going to fix it. You will need at least 40 dB of attenuation and to my knowledge none of the commercially available filters will do the job. I heard that Array Solutions might have a transmit HPF now but I have not looked into it. 73 Hardy N7RT - Original Message - Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! Though I would asking before placing an order, not sure how what to look for with BCB interference ? Tnx Ed N5DG _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Matching network info for 80 160M needed
If the inverted L is made to be 3/8ths wave long on 160 meters it can be feed as a 3/4 wave on 80 meters. In this case only a series capacitor to tune out the TB inductive reactance is needed on 160 meters and a shorting switch for using the same wire on 80 meters. A large open frame relay should sufficient unless you are running super QRO. Herb Schoenbohm, KV4FZ On 9/22/2014 12:48 PM, Gary Marks wrote: I have an Inverted-L antenna for 80M 160M and would like to make or buy a remote matching system that would work on both ends of both bands that would accept full power. I built a system many years ago from a Doug DeMaw, W1FB, article in the May 1985 issue of QST but it has never worked as well as I wanted for whatever reason. If anyone is interested, this article can be found at the ARRL QST archives http://www.arrl.org/arrl-periodicals-archive-search by entering W1FB , 1985, May, QST. Anyone have an idea of a matching system that would do all of the above ? _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
I had a local BC station start to produce spurs that overloaded an external preamp for my full size RX flag. The Array Solutions W3NQN RX filter did the job. I tried an Array Solutions AS-402 BCB High Pass Filter but it doesn’t have the brick wall response of the W3NQN design. For all I know, my local BC station is still malfunctioning. The Clifton Lab design looks as if it should work comparably to the W3NQN filter. The Array Solutions AS-RXFEP front end protector should be consider if your RX and RX antennas are close and your run QRO. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
On 9/22/2014 9:42 AM, Jim Brown wrote: On Mon,9/22/2014 7:07 AM, Hardy Landskov wrote: The catch is it has to be able to handle the transmit power too. Not if you put the filter in the RX loop. That feature is part of the KXV3 and KXV3A modules 73, Jim K9YC Does this allow me to listen on my transmit vertical through a low power high pass filter? AFAIK, what you are talking about only applies a filter to the separate RX antenna. I tried to read about this on the Elecraft site, but it is not clear. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
It operates like a send/return loop. You can toggle the signal routing from the front panel to either use the external device or not. I know for a fact it will work for the transmit antenna since that's what I use it for, but as far as I know it can be used for *any* external antenna, but not the separate receive antenna (using the separate connector) you can have for the KRX3. Elecraft uses this same setup to put their 6m preamp inline (which is where I first found out about it -- the preamp mounts to the back of the radio with dual BNC connections). The manual discusses using the loop to allow external filters/amps to be patched in. -Bill Not if you put the filter in the RX loop. That feature is part of the KXV3 and KXV3A modules 73, Jim K9YC Does this allow me to listen on my transmit vertical through a low power high pass filter? AFAIK, what you are talking about only applies a filter to the separate RX antenna. I tried to read about this on the Elecraft site, but it is not clear. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
On Mon,9/22/2014 6:50 AM, Ed Stallman wrote: Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html The spec for this filter is ambiguous. Is the -40dB at all frequencies below 1.6 MHz, or at 1 MHz? BIG difference. OTOH, the Dunestar filters are decent for the price. I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! That may be because they are transmitting digital radio. No filter will remove that -- it's part of their sidebands. Thought I would asking before placing an order, not sure how what to look for with BCB interference ? A year or so ago, I reviewed a bunch of bandpass filter sets designed for contesters. I also measured an ICE BCB filter (160M highpass). k9yc.com/BandpassFilterSurvey.pdf The pdf includes a link to pdfs of the VNWA data. I measured the filters that I either owned or could borrow from local NCCC members. Sorry -- the ICE BCB was the only one I had access to. I didn't put a marker at 1.5 MHz (I would have, but I was out of markers), but eyeballing it without a marker, I'd say that all of these filters (except the ICE419Bs) would be down by at least 15 dB at 1.5 MHz. The ICE BCB was about -16 dB at 1.5 MHz. 15 dB would reduce that 25kW station to 800W. Maybe enough, maybe not. For more rejection, you'll need one of the W3NQN designs that Array Solutions sells. And remember that NO filter will touch any sideband trash that the station puts on 160M. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
On Mon,9/22/2014 11:09 AM, Richard (Rick) Karlquist wrote: On 9/22/2014 9:42 AM, Jim Brown wrote: On Mon,9/22/2014 7:07 AM, Hardy Landskov wrote: The catch is it has to be able to handle the transmit power too. Not if you put the filter in the RX loop. That feature is part of the KXV3 and KXV3A modules 73, Jim K9YC Does this allow me to listen on my transmit vertical through a low power high pass filter? Yes. The KXV3 and KXV3A give you the output of the T/R switching and the input of the RX, so that you can loop that through the filter. AFAIK, what you are talking about only applies a filter to the separate RX antenna. I tried to read about this on the Elecraft site, but it is not clear. The multiple ways in which a K3 can be configured contribute to the confusion. :) If you have the second RX and the antenna tuner, you will have an AUX input (a BNC) that can be the alternate antenna for the second RX. That's a choice you make when installing those modules, and that's how my K3s are set up. My Beverages feed that AUX input, and are also wired in parallel to the RX input, so I can listen on the Beverages on the Main RX if I want to. I also have a 6M preamp that I switch into that RX loop using a Top Ten relay box. Here in the Santa Cruz Mountains, I'm not close enough to any AM stations to need a BPF. It was a different story in Chicago, with five 50kW clears within 20 miles and a kW or two within a mile. :) 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Matching network info for 80 160M needed
Hi Gary, there was an article in recent issue of ARRL QST, A 20 and 40 meter Vertical on Autopilot, from QST september 2005 by Dan Richardson, K6MHE...same article ended up in ARRL More vertical Antenna Classics :) Use heavy duty compononets, treat 160 m vertical as 1/4 lambda and 80 meters as 1/2 lambda...let us know :) You might have followeres.. Kr Nermin S58DX - Original Message - From: Gary Marks gma...@neo.rr.com To: Topband topband@contesting.com Sent: Monday, September 22, 2014 6:48 PM Subject: Topband: Matching network info for 80 160M needed I have an Inverted-L antenna for 80M 160M and would like to make or buy a remote matching system that would work on both ends of both bands that would accept full power. I built a system many years ago from a Doug DeMaw, W1FB, article in the May 1985 issue of QST but it has never worked as well as I wanted for whatever reason. If anyone is interested, this article can be found at the ARRL QST archives http://www.arrl.org/arrl-periodicals-archive-search by entering W1FB , 1985, May, QST. Anyone have an idea of a matching system that would do all of the above ? _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Date: Mon, 22 Sep 2014 11:21:29 -0700 From: j...@audiosystemsgroup.com To: topband@contesting.com Subject: Re: Topband: BCB interference ? On Mon,9/22/2014 6:50 AM, Ed Stallman wrote: I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , is that close enough to interfere with me receiving weak signal DX on the top Band ? I do hear some wide band hash 1837 to 1840 ! And Jim Brown wrote: That may be because they are transmitting digital radio. No filter will remove that -- it's part of their sidebands. 73, Jim K9YC Jim: Digital sidebands for AM stations only extend +/- 15 kHz from the carrier. If noise is being heard 317 kHz above the carrier, it's not due to IBOC usage. Chuck _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Matching network info for 80 160M needed
On 9/22/2014 9:48 AM, Gary Marks wrote: I have an Inverted-L antenna for 80M 160M and would like to make or buy a remote matching system that would work on both ends of both bands that would accept full power. I have a 90 foot top loaded vertical on 160 meter that is resonant on 1830 with just the top loading wires. If I measure the impedance of it on 80 meters, it is somewhere around 1000 ohms and resonant somewhere in the 80 meter band. It would be possible to build a dedicated match for each band and then switch between them. The component values are so vastly different that you need separate networks. What I actually do is have a relay at the 60 foot point in the vertical that disconnects the top 30 feet of the antenna for 80 meters. MUCH simpler than matching to ~1000 ohms. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Their description (to me at least) indicates an elliptic filter with a stopband peak of -40 dB at 1 MHZ and ranging to infinity (in theory) elsewhere in the stopband. In other words, 40 dB is the maximum for the discrimination factor. Indicates is a word I feel is necessary as their filter really is poorly described. They should have said what filter type and order are used and used standard nomenclature for filter parameters. And there's no mention of passband ripple. Chuck Date: Mon, 22 Sep 2014 11:21:29 -0700 From: j...@audiosystemsgroup.com To: topband@contesting.com Subject: Re: Topband: BCB interference ? On Mon,9/22/2014 6:50 AM, Ed Stallman wrote: Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html The spec for this filter is ambiguous. Is the -40dB at all frequencies below 1.6 MHz, or at 1 MHz? BIG difference. OTOH, the Dunestar filters are decent for the price. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
I have a 50 KW station on 1530, eight miles north of me. They have a six element in-line array aimed south at Mexico... and me. They tore up every rig I've had in the shack until I went to a K3. We have two K3s and have no problem on either of them with BCB other than weak birdies on 1820 and a few other multiples of ten on 160 and 80. Rigs like the IC7000, and the FT857, a TS850s and others have hash from that station across the whole HF range. Even the TenTec Omni 6+ was plagued with junk everywhere. Many years ago I borrowed a commercial sharp-knee hi-pass filter from AA1K. I forget who made it but you could ask Jon. It may have been a NQN unit. The filter was made to take the power output of a 150 watt rig. That did the job for most all rigs. I duplicated the filter and made a couple of them for use in this environment. I tweaked the toroid coil spacing and parts positions until there was a cliff starting about 1790 and the transmit loss was minute across 1.8 to 30 mHz. I built in my own sharp-knee filter in the Omni 6+ and added a suck-out filter tuned to 1530. That fixed the TenTec. In more recent times, The problem became critical when I installed the HI-Z four element receiving array. Those Plus amps at the base of each element were sitting ducks for all that broadcast RF. The birdies were 20 over 9 and the sidebands covered 12 kHz! Lee, K7TJR at HI-Z made up four matched input traps for the amps and that brought down the problem to barely a nuisance. I won't miss any contacts because of it. We don't use any internal or external filters on the K3s and I'm surprised that you are having trouble with yours. There has to be an answer to explain that. The BCB RF is so strong here that our land line was always providing the programming from KGBT. BTW, it's a 24 hour talk radio station in spanish. We went to all cell fones a few years ago. CU on Topband, 73, Barry, W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
Pardon me, but an elliptic filter does not tend toward infinite attenuation in the stopband! The tradeoff, with elliptical filter designs, in which we incorporate transmission zeroes to increase the cutoff rate into the stopband, is finite attenuation in the stopband. Indeed, ultimate attenuation and ripple are essential specifications that must be incorporated into the design of an elliptical filter. If really high values of attenuation are required the elliptic filter can be followed by Butterworth or other all-pole filter section(s) 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Chuck Hutton Sent: Monday, September 22, 2014 3:22 PM To: topband@contesting.com Subject: Re: Topband: BCB interference ? Their description (to me at least) indicates an elliptic filter with a stopband peak of -40 dB at 1 MHZ and ranging to infinity (in theory) elsewhere in the stopband. In other words, 40 dB is the maximum for the discrimination factor. Indicates is a word I feel is necessary as their filter really is poorly described. They should have said what filter type and order are used and used standard nomenclature for filter parameters. And there's no mention of passband ripple. Chuck Date: Mon, 22 Sep 2014 11:21:29 -0700 From: j...@audiosystemsgroup.com To: topband@contesting.com Subject: Re: Topband: BCB interference ? On Mon,9/22/2014 6:50 AM, Ed Stallman wrote: Has anyone used this High Pass Filter ? http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html The spec for this filter is ambiguous. Is the -40dB at all frequencies below 1.6 MHz, or at 1 MHz? BIG difference. OTOH, the Dunestar filters are decent for the price. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
I have a three-frequency 2.7KW BC station that is 350 yards from the base of my 160m vertical. The NQN BCB filter knocks out all problems - well except for the 2nd harmonic of the 945KHz feed which sometimes turns up for a day or so. I can't think of a single reason not to try one if you have BCB, they are cheaper than almost any rig accessory you're likely to buy! 73 Chris, G3SVL _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: BCB interference ?
On Mon,9/22/2014 5:51 PM, ch...@g3svl.com wrote: I can't think of a single reason not to try one if you have BCB, they are cheaper than almost any rig accessory you're likely to buy! Their effectiveness will depend entirely on the frequencies within the BCB you are trying to suppress. 945 kHz is FAR easier than 1530 kHz, which is what these guys are dealing with. Yes, the ICE BCB works fine down around 1 MHz, but it doesn't have nearly enough poles to suppress a very big signal at the top of the band. There's a link to my measured data for my BCB in that filter review for which I posted the link. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Beverage antenna isolation measurements
I have just finished installing 6 Beverage antennas in the woods north of my house. Details are below. My question to the group involves measuring the isolation of these antennas from my transmitting antennas. I am testing by transmitting on all bands with either 100 or 500 watts and simultaneously measuring RF levels on the Beverage feedline in the shack. Eventually I want to set up an SO2R station. To measure the power, I am using a homebrew RF power meter kitted by Kanga and based on the AD8307 (QST June 2001 - W7ZOI and W7PUA). This is a 50 ohm instrument and I feed the Beverages with 75 ohm RG-6. This means a nominal VSWR of 1.5:1 (14 db return loss). I placed an ICE Model 401 bandstop BCP filter in front of the meter. The raw results look good with the worst isolation to date being 65 db, i.e. 160 microwatts while transmitting with 500 watts. I have some more measurements to finish with the triband yagi aimed in a few different directions. How much inaccuracy is there in this method due to the 75/50 ohm mismatch at such low power levels (16 nanowatts to 160 milliwatts)? Is there an easy mathematical correction (for a guy who took calculus 39 years ago) for the impedance mismatch or does it matter? Beverage antenna details: (map of Beverages is on my QRZ.com page) My Beverage antenna project is completed and the 6 antennas seem to work well. They are between 470 and 860 feet long so as to stay on my property and radiate from a central hub. I used 17g galvanized fence wire 7 feet high held up with plastic fence insulators nailed to trees. They point to 40, 80, 160, 240, 280 and 340 degrees. I terminate them with Ohmite 470 ohm 2 watt resistors. The transformers are the usual 6.25:1 (5T,2T) on a BN73-202 core. Four foot ground rods are driven at the ends of each Beverage. There is 20-30 feet of RG-6 coax from the transformers to the homebrew switchbox. I use 24v relays (RK1-24V) and run almost 600 feet of CAT5 for a control line. Unused antennas are not grounded. The RG6 feedline goes about 30 feet from the switch towards the shack where the braid is grounded. I put a K9YC choke (8 turns of the RG-6 wound around a #31 Big Clamp-On) on the shack side of the braid ground and then the coax runs almost 600 feet back to the shack. I ground the braid again just outside the shack. In the shack is a homebrew switch box containing a 24v linear power supply and a 7 position rotary switch. (The 7th position is labelled for an external switch when I get around to building one similar to LA4HIA). Thanks for reading this verbose question. I spared readers the details of cutting paths for these antennas totalling 4090 feet through woods infested with an understory of invasive European buckthorn, multiflora rose, and honeysuckle. Of course it was done in the hottest, most humid and most mosquito infested part of our late summer. 73, Charlie W2GN _ Topband Reflector Archives - http://www.contesting.com/_topband
