Re: Topband: Waller Flag Question

On a totally unrelated note, I cascaded two preamps to get 40 dB of gain about 30 years ago. They were identical circuits, both using MGF-1202 GaAs FETs. The input was a Zener diode noise generator. The second preamp fed a 3dB splitter which fed two inputs of a low-loss passive nulling circuit I

Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

Oops, I forgot to sign my prior email... 73 Frank W3LPL - Original Message - From: donov...@starpower.net To: "PVRC" , cq-cont...@contesting.com, topband@contesting.com Sent: Tuesday, September 8, 2015 6:41:14 PM Subject: The first indicators that Solar

Topband: Waller Flag

I must be missing something. The noise in a 50 ohm resistor is -174 dbm per root Hz at ambient temp. Lets take 100Hz bandwidth for the receiver and the noise becomes -154 dbm or .0045 uVolts Lets add a PERFECT amplifier of 40 db. The noise output of the 40 db amp is then -114 dbm or 0.446

Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

That's not so good news for 160, eh? 73, Mike www.w0btu.com On Tue, Sep 8, 2015 at 1:41 PM, wrote: > ... some solar scientists feared that Solar Cycle 25 might achieve a much > lower amplitude than Cycle 24. Those fears might now be put to rest. > _

Re: Topband: Waller Flag

Lee Yes, this is confusing as it can get. Any passive component adds noise, any active components adds noise. Power noise, and you only can add power noise converting it in equivalent temperature in Kelvin degree. The antenna itself is another confusing thing, any antenna has directivity gain

Re: Topband: Waller Flag

On 9/8/2015 1:01 PM, Lee K7TJR wrote: To me a signal of 79 uVolts is something over S-9 on a receiver. Would a simple dipole or inverted Vee antenna with essentially no gain produce a whopping signal from the same source. Of course it would pick up noise as well but I would think it would not

Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

Not really a problem for 160. Solar minimum is a solar minimum is a solar minimum. In the last solar minimum a certain well known multi-multi in one of the major CW DX tests did a single weekend five band DXCC 160 through 15 meters. I think that's the only time that's ever been done. Great ops

Re: Topband: HMC580 instead of W7IUV preamp

Given the recent discussion about the need for low-noise preamps for the Waller Flag, it would be interesting to learn what the NF on 160 for this device might be. It's rated for "DC" up into the GHz range. However, as N4IS pointed out, a good NF at VHF does not mean a good or better NF below 2

Re: Topband: Waller Flag Question

Pardon me for chiming in on this Waller flag discussion as I am probably the least qualified person on Topband to discuss technical issues. But, I do a lot of Trial and Error-ing and use some of the wisdom shared here. Plus I am a true Ham O Holic and always want to improve my ability to work

Re: Topband: Waller Flag

After putting my conclusions here and a 2 1/2 hour power outage I had an aha moment and found I did not account for 40 db properly. The dipole without a preamp in the same location is just a few db higher than the Waller with preamp and would not produce the signals I was thinking of. Lee

Re: Topband: [WARNING: ATTACHMENT(S) MAY CONTAIN MALWARE]RE: Waller Flag Question

I meant OFF and not ON for the internal preamp. I don't use internal preamp ON. The issue is most internal preamps are not designed for 160m, they need to cover up to 50 MHz Even the ICOM Norton preamp does not have the muscle to handle the signals level on 160m. If you turn << OFF >> you

Re: Topband: Waller Flag Question

Tom, I'm afraid I disagree but agree with some of that, I am using a 43dB gain preamp since 2010 with not a single failure yet, but I understand your point. It is so delicate to implement that most of fellow that try it fail. Even aluminum enclosure does not shield it enough, 40 dB gain is

Topband: [WARNING: ATTACHMENT(S) MAY CONTAIN MALWARE]RE: Waller Flag Question

>> A 0.5 dB noise figure front end amplifier with NO other losses would produce -149.5 dB MDS. That is the absolute maximum MDS sensitivity obtainable with 250 Hz BW and 0.5dB total input noise figure. << Correct agree >> If we include the receiver's noise figure, 14.5 dBm gain would result is a

Re: Topband: Waller Flag Question

Above and beyond all the dialogue, JC is making these antennas work. Time after time he is working stations that only a few with large antenna systems copy.   73 Bruce-K1FZ           It seems unlikely most compact antennas are being used in locations so quiet they need 30 dB gain, or .6 dB

Re: Topband: Waller Flag Question

There seems to be something that I'm missing in this preamp NF discussion. When I studied preamps and NF ~30 years ago, I thought the NF of the system of the first active device was the all-important thing. Whatever losses were between the antenna feedpoint and the preamp input (coax, connectors,

Re: Topband: Waller Flag Question

There is no question in my mind that he is, Bruce. I would just like to understand what Tom is saying. I almost think he had noise figure confused with noise temperature at one point. Correction to my previous e-mail, first sentence in second paragraph. should have said "When I studied preamps

Re: Topband: HMC580 instead of W7IUV preamp

On 9/8/2015 7:02 PM, Mike Waters wrote: Given the recent discussion about the need for low-noise preamps for the Waller Flag, it would be interesting to learn what the NF on 160 for this device might be. It's rated for "DC" up into the GHz range. However, as N4IS pointed out, a good NF at VHF