----- Original Message -----
From: "Lee Buller" <k0wa@swbell.net>
To: "CQcontest Reflector" <cq-contest@contesting.com>
Sent: Wednesday, January 23, 2008 10:00 PM
Subject: [CQ-Contest] SO2R Technical Question - Round II
>
> After reading quite a bit on the WWW about SO2R....
>
> I am assuming that you place band pass filters (what ever
> ilk) in line with BOTH radios. That being the case (if it
> is) then using bandpass filters on 40 you would be
> knocking down (but not eliminating) the harmonics on 20
> meters.
and eliminating the broadband noise that synthesized radios
transmit both below and above the band they are transmitting
on.
> In addition if you have a 20 meter filter on your second
>radio, that do would have attenuation on the 7 Mhz energy.
>So if the transmit filter on 40 is...say....40 db down and
>the receive filter on the 20 meters station is another 40
>db
>down....would not those figures combine? That is a
>question!
Not really. The second harmonic of 40 might be 40 dB down,
but the 20 meter bandpass filter won't reduce the harmonic
any more, because it is in-band.
Conversely, the 20 meter BPF will reduce the 40 meter
fundamental by 40 dB, but there will be no further additive
reduction by the 40 meter bpf on the transmitter. This is
the
case you've really got to worry about. You've got to get to
the point where you can transmit 1500 watts on 40, and not
feel the slightest tingle on your damp finger when you
lightly
touch the PL-259 going to the other radio.
> That means you would have to have filters for 6 bands
> times 2 or 12 filters. if you were running 160, 80, 40,
> 20, 15, and 10 meters. I guess you could use a manual six
> position switch to select the Radio 1 filter and the Radio
> 2 filter. That would mean using passband filters...that
> you would need to switch the filter to the band you were
> on and all is well. Now, alot of S02R ops use automatic
> switchers (I am sure they found that to be less expensive
> in the long run that sending in the radio for
> repair)...but one could get away with the manual switch if
> you were "careful." This is only a good way of doing
> things if it is a bandpass filter.
>
You could get away with six single-band filters and keep
switching them between radio 1 and radio 2, but that is a
very inefficient way of operating. You wouldn't be happy
with it for long. For operational reasons people eventually
settle on two 6-band filter boxes.
You can do a manual switch on BPF's if you leave the antenna
tuner OFF. SWR protection on the transceiver will protect
the
BPF. If you ever press the tuner TUNE button, all bets are
off.
Dave Hachadorian, K6LL
Yuma, AZ
.
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|