Topband: Which compromise receiving antenna

[Peter]

Hi

Here at PI4CC we are busy with building a 9 circle array.
And our motto is DIY so we have create a PCB for the RX preamp around 
the AD8055 ala the YCCC

Some details are at https://www.pi4cc.nl/tech-info/rx-array/
The page will be update later since it is an on-going project

Peter
Op 7-11-2018 om 2:40 schreef John Kaufmann:
> I designed the YCCC preamp so I can answer the question about the AD8055 op
> amp.
>
> As used in the YCCC preamp, the linearity is actually very good.  We use a
> YCCC receiving array at KC1XX in a multi-operator, multi-transmitter
> environment with 20 foot receive verticals.  That's a pretty severe RFI
> environment.  When listening on the array on either 160m or 80m, there is
> absolutely zero interference or other noticeable degradations from
> out-of-band transmitters.  When listening with an in-band transmitter, there
> is a lot of noise near the transmitter frequency, but most of it is phase
> noise from the transmitter itself.
>
> If you want more technical detail, here are some of the considerations
> behind the choice of the AD8055.  First of all, the YCCC preamp is a kit.
> Based on that consideration, I ruled out surface mount op amps that
> inexperienced kit builders might not be comfortable with.  In truth there
> are some truly outstanding surface mount parts with much better performance.
> The AD8055 comes in a standard 8-pin DIP package that's easier to work with
> and it was the best 8-pin DIP part I could find.  It is intended
> specifically for use in RF systems.
>
> Second, the preamps must exhibit very accurate gain and phase matching to be
> used in a multi-element active array.  The YCCC preamp meets this
> requirement because it operates with unity voltage gain in a negative
> feedback configuration that virtually guarantees extremely accurate gain
> setting.   There is no trim adjustment needed at all for gain.  I have done
> VNA measurements on many of these preamps built by different people and
> every single one of them, when assembled correctly, exhibits a gain accuracy
> of +/-0.1 dB gain and better than one degree of phase matching accuracy
> across 160 and 80.  The large amount of negative feedback used at unity gain
> also contributes directly to low distortion.
>
> I don't have test equipment to perform accurate distortion measurements.
> However, the AD8055 datasheet does have data on second and third order
> harmonic distortion figures that look very good at 1.8 through 4 MHz.  In
> fact these distortion levels are similar to what you might see in a high
> quality stereo audio amplifier.
>
> Having said all that, prospective system builders should be aware that DX
> Engineering has just discontinued sales of the YCCC preamps as the entire
> inventory of these kits has been sold out.  Once their inventory of phase
> combiner and direction switch kits is sold out, those will also be
> discontinued.  YCCC, as a club, has no intention of selling kits.
>
> 73, John W1FV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Tuesday, November 6, 2018 3:17 PM
> To:donovanf at starpower.net; topband reflector
> Subject: Re: Topband: Which compromise receiving antenna
>
>
> I am puzzled by the choice of the AD8055 for the amplifier.
> It seems to be unprepared for strong BCB signals.  Has
> anyone successfully used this near a BCB station?  I am
> 6 miles from a 50 kW station.  It seems to me there are
> much better amplifiers available.  Or why not a FET follower?
>
> Rick N6RK
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