Topband: Hi Z amplifiers for 160m

[Lloyd - N9LB]

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.net at contesting.com] On
Behalf Of Lee STRAHAN
Sent: Wednesday, March 11, 2020 12:17 PM
To: topband at 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 +0000
  Chris Moulding <chrism at 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
>
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