[hpsdr] Pennywhistle capabilities question

[Dave Watson]

Thanks for the quick reply George. I thought that was the case. I really
like the PennyWhistle so I think it will be worth and additional controller
board to switch the RX/TX on both sides (DPDT). 

Dave (W4DJW)

-----Original Message-----
From: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of george byrkit
Sent: Sunday, September 04, 2011 1:20 PM
To: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Pennywhistle capabilities question

***** High Performance Software Defined Radio Discussion List *****

Dear Dave,
The PennyWhistle is a transmit-only device.  You would not be able to get an
RX signal back thru it.

Typically, the RX/TX commutation device referred to by Roland is called a
'T/R switch'.  Gerd has them for sale, and Alex includes one as well.   But
for reasons explained below, I don't think either is appropriate for you,
currently.

The PennyWhistle works best in a situation like PennyLane (or Penelope) and
Mercury, where each has its own antenna connection.  Thus, a T/R switch
after PennyWhistle works well to switch the antenna to TX (signal from
Penelope thru PennyWhistle to antenna) or RX (antenna connected to Mercury).
With something like a SoftRock, where there is only one antenna connection,
you need a more complicated T/R switch (DPDT, rather than SPDT, and isolated
sections for the DPDT) that can completely bypass PennyWhistle, while at the
same time likely terminating the input to PennyWhistle so that it won't see
a signal to amplify.  Floating inputs can be a problem!

Duplexers aren't very practical at HF frequencies, because of their large
physical size.  ALso, they are relatively narrow in bandwidth, say, compared
to 1.6mHz thru 50mHz.  They are also a better fit, say, for a repeater,
where there is simultaneous TX and RX (albeit at somewhat different
frequencies!), and the TX and RX have separate antenna connectors.

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