Thanks, Rick. I think you are fortunate to have a low noise level where you could actually use your TX Antenna.
My situation is that if I tried to listen on my transmit antenna I would only work the very strongest of signals. Typically the noise moves the meter to about 20-25 over S9 if I listen on my vertical. The best success I have had is with a Beverage, but whether on any given trip I can put one up largely depends on whether any of the four or five people's property I would cross are there and whether they would allow it or complain about it. On my own property, the only thing I have done is put up a little triangle with the top at about 20 feet and the bottom wire in the neighborhood of 30-35 feet. That antenna has about -37 dB of gain. A 15 dB preamp plus the preamp in the transceiver makes it an OK antenna - good enough that I have worked about 250 JA stations none of which would have been worked if I were listening on my vertical. And I am guessing that if I had a 3 dB improvement in S/N ratio that I would have worked 400 in the same time period. That antenna has an RDF of 7.7. Always wanting something better and if I could put up something I could rotate with an RDF of 11 or so, I would hope to be content. Stan Stan On Sat, Dec 15, 2018 at 1:47 PM Richard (Rick) Karlquist < rich...@karlquist.com> wrote: > General response, not specific to the Waller Flag: > > For a number of good reasons, you should not expect > a NF below 3 dB for any practical preamp. OTOH, > virtually all radios have an internal switchable preamp. > Let's say your radio is really pedestrian, and the > internal preamp has 10 dB NF. Neglecting feedline > loss, your preamp gain only needs to be about 13 dB in > order to the preamp noise to dominate over the radio > noise. Any additional gain above that will not help > you "start to hear band noise" but will instead hear > preamp noise. Some ops like to use additional gain in > the preamp to make the AGC threshold occur at a lower > level. This reduces listener fatigue, but does not > actually produce any newly-readable signals. > > If the above isn't correct, can someone give a worked > example of where a 40 dB preamp would make sense? > > FWIW, I tried a Waller loop last year in the 160 meter > contest. It was quite large (I have plenty of space). > It seemed to be working OK in terms of being directional, > but it almost never improved the readability of any > signals vs the vertical. IOW, aiming it at Japan didn't > help work JA's, except to the extent that it reduced > stateside QRM. On a clear frequency, there was no advantage. > > 73 > Rick N6RK > > On 12/15/2018 11:15 AM, Stan Stockton wrote: > > I am curious to know if anyone on here has scaled a Waller Flag to a > > smaller antenna and had any success with whatever might be available for > > preamps to bring the gain up enough to start to hear band noise. > > > > At my location on Cayman Brac I could probably get by with a 20 foot boom > > but not much larger. According to my model, one with a 50 foot boom is > > about -48 dB, one with a 30 foot boom is about -65 dB and one with a 20 > > foot boom, like I would lilke to put up, is about -79 dB. > > > > I guess a lot to do with how successful the antenna might work for me > will > > have to do with how much preamplifier gain I will need at my particular > > location to start to hear noise. I wanna use it on 160, 80 and 40 and > the > > gain of the 20 foot boom one is enough for 80 and 40 using a 30 or 40 dB > > preamp. > > > > Any help would be appreciated. > > > > 73 and Merry Christmas...Stan, K5GO/ZF9CW > > _________________ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > > > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector