George,
Thanks for your response. In my situation the commercial option is what I can
best manage. I have several other KD9SV designs and they have been great.
Tim, thanks for the choke suggestion.
73
W7TMT
From: GEORGE WALLNER <aa7jv@atlanticbb.net>
Sent: Thursday, October 3, 2024 18:43
To: W7TMT - Patrick <W7TMT@outlook.com>; ws6x.ars@gmail.com;
topband@contesting.com
Subject: Re: Topband: E51D Oct 1
Hi Patrick,
This is a custom unit that I built. While this version would be very difficult
to reproduce, there are some commercial pre-amps that come close. Specifically,
the DX engineering SV-BF-99X5 by KD9SV, (Just set the gain to 20 dB. Don't
bother with higher gain as the noise figure gets worse.) In my case, I put the
pre-amp into a small Pelican case along with a bias T (100 nF series C and a100
uH and a 47 uH inductor in series.) I have also added a GND terminal to the
line end (to output side that goes to the receiver) which, in combination with
a choke (#31 core with 8 turns of coax) ensures that noise travelling on the
outside of the coax does couple into the antenna. Whether you use 50 Ohms and
75 Ohms coax is entirely up to you. Just make sure the connectors are good and
well sealed against moisture.
I you want to reproduce my pre-amp, I am happy share the circuit diagram, but
even I would not try do it again!
GL and LMKO if you need more info.
73,
George
On Thu, 3 Oct 2024 23:26:30 +0000 W7TMT - Patrick wrote:
George,
If you have a moment a few more details about the feed-point amplifier would be
appreciated. Is this a custom unit or an of-the-shelf commercial unit please?
Thanks for your time.
Patrick, W7TMT
________________________________
From: Topband
<topband-bounces+w7tmt=outlook.com@contesting.com<mailto:topband-bounces+w7tmt=outlook.com@contesting.com>>
on behalf of GEORGE WALLNER
<aa7jv@atlanticbb.net<mailto:aa7jv@atlanticbb.net>>Sent: Wednesday, October 2,
2024 7:55:20 PMTo: ws6x.ars@gmail.com<mailto:ws6x.ars@gmail.com>
<ws6x.ars@gmail.com<mailto:ws6x.ars@gmail.com>>;
topband@contesting.com<mailto:topband@contesting.com>
<topband@contesting.com<mailto:topband@contesting.com>>Subject: Re: Topband:
E51D Oct 1
Thank you Wes, but it wasn't my "ears" (which are not what they are used to be)
but a new RX antenna and a very low noise pre-amplifier, that we installed
yesterday morning. Your signal was an easy copy with this new antenna. There
was no trace of it on the TX antenna! (You also set your frequency well: a
couple of hundred Hertz away from the other callers but still withing the RX
passband.) There is a timely thread going on about a "Low Frequency RX
Antenna". The antenna we installed yesterday is a single support variant of
this VE3DO loop, which is essentially a delta loop. This type of antenna is
easy to install and gives you an RDF that is just a few of dB-s shy of a small
Beverage, but at a much lower gain. The key is a low noise amplifier located at
the antenna. This is a must in almost all situations. The amp is remote not to
overcome the coax losses (which it does), but to ensure that amplification
takes place before noise is introduced into the RX system. We have a single RI
B on a small cay with two Honda 22i generators. Like most temporary
installations, grounding is less then perfect and some noise couples into the
RX circuit. A low noise pre-amp at the antenna, turns a -30 dBi RX antenna into
a -10 dBi RX antenna with an RDF of 7 dB. That is sufficient to overpower the
noise that inevitably gets into the receiver. I will be on TB again tonight.
73, George, E51D PS: You can easily expand this antenna to cover four
directions by adding a second loop on the same support at 90 degrees, and use
switchable transformers to change directions. On Wed, 2 Oct 2024 11:12:43 -0400
wrote: >As a tribute to George's incredible ears on E5-N, this morning, at
1107 UTC, >just before local SR, I worked E51D QRP, using a "nothing special"
Inv-L. >This is from Northwest Rockingham County, VA, FM08. The signal was
solid >copy, averaging around S7. Signal strength was not quite as loud as 2
days >prior, when peaks reached nearly S9. >Oddly, yesterday, morning, on FT8,
I c
ouldn't work E51D with a kW! >Thanks, George. >Jim - WS6X _________________
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