Topband: Thanks to K3LR and DX Engineering! (Was: RE: DX Engineering 4-Square RX Antenna: Element Amplifiers?)

[john]

yes,, says a lot,, a whole lot for dx engineering    73 john

On 9/24/2015 4:58 PM, Jeff Maass K8ND wrote:
> Thanks to all who replied with suggestions and information!
>
> Tim Duffy K3LR responded on behalf of DX Engineering, and offered to have
> our 4-square amplifiers checked-out and calibrated to match within +/- 0.1
> dB. They are also going to look at the DXE-RFS controller to assure that it
> is functioning correctly to switch the delay lines and antenna feeds when
> commanded. All this at no cost to us, including shipping!
>
> Thanks to Tim and to DX Engineering for this fantastic response!
>
> We've been using the DXE 4-Square RX antenna system at PJ2T since 2006. When
> operating on 160 and 80-meters from just 12 degrees North of the Equator,
> receiving antennas that work are very important.   The DX Engineering
> antenna has been an important resource in some very successful PJ2T CQWW CW
> and CQWW 160 CW Contest operations, including four consecutive 1st Worldwide
> finishes in the CQWW 160 CW Contest.
>
> Thanks again, Tim K3LR!
>
> 73,  Jeff  K8ND
>
>   
>
> From: Jeff Maass K8ND [mailto:jmaass at k8nd.com]
> Sent: Tuesday, September 22, 2015 9:17 PM
> To: 'cq-contest at contesting.com' <cq-contest at contesting.com
> <mailto:cq-contest at contesting.com> >
> Cc: 'Jim Galm (jim at w8wts.com <mailto:jim at w8wts.com> )' <jim at w8wts.com
> <mailto:jim at w8wts.com> >
> Subject: DX Engineering 4-Square RX Antenna: Element Amplifiers?
>
>   
>
> In January, Jim W8WTS and I were at PJ2T for CQWW 160 CW, and we both noted
> that our DX Engineering 4-square RX antenna did not appear to perform as
> well as usual. It is a 98-foot configuration using 102-inch whips.
>
> It is set up "field day style" for contests when we use it (i.e. not set up
> permanently), and so we thought that perhaps all the handling over the years
> might have caused problems with the feed and delay cables. We had a Array
> Solutions AIM-4170C VNA with us, and confirmed that all the cables were
> still  in good shape and were of the correct lengths.
>
> We decided to bring home the four DXE ARAV3 active antenna amplifiers to
> diagnose at home (we left the four whips on Curacao!). W8WTS has an Array
> Solutions VNA-2180 2-port device, and captured curves for inputs and
> outputs. His analysis is shown below. Screen captures of the resulting
> curves are in an archive at:
> http://www.k8nd.com/Radio/PJ2T_DXE_4-Square_amps_ photos.zip
> <http://www.k8nd.com/Radio/PJ2T_DXE_4-Square_amps_%20photos.zip> .
>
>   
>
> "Each amp has a port a sweep and a port b sweep.  There is also a reference
> pair of sweeps with the amplifier jumpered out of the circuit, to verify
> that the ports are calibrated correctly.  The port a sweep shows the
> impedance looking into the antenna port.  We want the input impedance to be
> extremely high; higher is better.  There is a peak in the Z because of the
> parallel LC filter on the input of the AVA-2 that rejects out of band
> signals.  You can see that they are all set correctly to peak on 1.8 Mhz.
>
>   
>
> "The port b sweep shows the magnitude and angle of S21.  S21 is the forward
> voltage gain of the amplifier.  We want the forward voltage gain to be
> exactly 1, which is shown on the graphs as 0 dB.  The four amplifiers have
> different gains at 1.8 MHz, but they are very close.  The lowest is amp 1 at
> 1.2 dB and the highest is amp 4 at 1.4 dB.  A gain difference of 0.2 dB is
> very small, but it might make a difference. "
>
>   
>
> They appear to be working OK, but what we don't know is:
>
>            QUERY: How much of a gain discrepancy is tolerable in the element
> amplifiers in a DXE four square?
>
> 73,  Jeff  K8ND
>
>   
>
>   
>
>   
>
>   
>
>   
>
>   
>
>   
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>