[WriteLog] Filters for two rigs and contesting

[Don Hill AA5AU]

Excellent URL's given by Keith.  I want to add something about
filters and stubs for two rigs.  I am a serious 2-radio RTTY contester.
I found a combination that works very well for me at my QTH where
I have antennas within inches of each other.  I use a combination of
Dunestar filters and stubs.

Forget the filters for a minute and think about the stubs.  For the
semi-serious contester you can get away with two simple stubs.  A
23' piece of RG-8 (Belden 8237) shorted at the end will allow you
to operate 15 and 40 meters on one radio.  On the other radio, a piece
of the same coax 23' long open at the end will allow you to operate
10 and 20 meters without changing stubs and will attenuate 15 and
40 meters.  It's a great combination which I have used for about a
year now with success. (2 RTTY world records).

Combining stubs and filters is, of course, the best scenario.  But if
you can't afford the filters, stubs work great and you don't have to worry
about the power limit.  For RTTY, there is interaction between 20
and 40 meters when the antennas are close together regardless of
stubs or filters because of the harmonics ( maybe the same for CW or SSB ).

But for years I have set up 2 radios - one for 15 & 40 and the other for
10, 20 & 80 and had great success.  With the addition of these simple
23' stubs (one shorted, one open) I have been able to nearly eliminate
any intra-station QRM between the radios despite the antennas being
practically on top of each other using the same band combinations.

For pictures of these stubs see:  http://www.geocities.com/aa5au/Shack.html

In the 2001 ARRL Roundup, I had no interaction between 20 and 40 meters
using both Dunestar filters and stubs.  However, in the 2001 WPX contest,
I did experience problems when operating those two bands at the same time.
I attributed it to rain and the antennas being wet, but I'm not convinced. More
filtering needed?  I don't know... the harmonics are so close.

Separation of RF on 20 and 40 meters will always be a challenge because of
harmonics.

73, Don AA5AU


----- Original Message ----- 
From: "Keith Regli" <keith@kregli.com>
To: <writelog@contesting.com>
Sent: Friday, June 29, 2001 5:18 PM
Subject: RE: [WriteLog] Filters for two rigs and contesting


> 
> Vince,
> 
> Check out the following websites for the relevant stuff:
> 
> http://www.arraysolutions.com/products.htm
> http://www.qth.com/dunestar/
> http://www.qth.com/topten/
> http://www.berkshire.net/~robbins/technote/techref.html#feed
> 
> The last has a lot of info on stubs in addition to designs for bandpass
> filters.  There was also a good article in NCJ, Jan/Feb 2000.
> 
> Keith Regli WB6BIG
> mailto:keith@kregli.com
> http://www.kregli.com/wb6big.htm
> 
> 
> > -----Original Message-----
> > From: owner-writelog@contesting.com
> > [mailto:owner-writelog@contesting.com]On Behalf Of VinceK6BIR@aol.com
> > Sent: Thursday, June 28, 2001 10:40 PM
> > To: writelog@contesting.com
> > Cc: digitalradio@yahoogroup.com
> > Subject: [WriteLog] Filters for two rigs and contesting
> >
> >
> >
> > I would like to know what is needed for operating two radios on different
> > band at the same time, what filters are used for this, I do know
> > when I am
> > transmiting on one rig the other gets blanked out, I do not have
> > any filters
> > between the rigs, so what does it take to do 2RSO in a contest.
> >
> > Tnx for any help
> >
> > Vince,  K6BIR
> >
> 
> 
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