I recall having similar issues with a similar setup years ago. You could
turn one of the antennas 90 off the other and see what the swr looks like
with the booms not parallel.
You might also want to take readings at the shack with a good meter. I have
also seen some erroneous readings with the mfj unit. My station is 5 miles
from KOA radio and 50kw!
Feedline lengths as suggested could be another area to look.
Mike
W0MU
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Tod - ID
Sent: Saturday, February 14, 2004 10:28 PM
To: 'Jim W7RY'; TowerTalk@contesting.com
Subject: RE: [TowerTalk] New Tower up With Some Issues 2L40 TH7
Just relax and feed the power to the system. Use a tuner to adjust the
impedance at the station for the 40-2CD when you use SSB. If the 2.5:1
bothers you at (21.000 you said, but I suspect you meant 28.000 MHz), then
use the tuner at the station to adjust that closer to 1:1 as well. These
adjustments will assure that the transmitter likes what it is attached to.
The only risk you have is that you will lose a little power in the feed line
if the SWR is 2.5:1 , but the amount lost will not be noticed by the guys
listening to your signal.
Your setup seems similar to mine (www.k0to.us) and your measurements seem
close as well.
The objective is to get power to be radiated, not to have the SWR be any
particular value. You seem to be in good shape.
Tod, KØTO
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim W7RY
> Sent: Saturday, February 14, 2004 6:27 PM
> To: TowerTalk@contesting.com
> Subject: [TowerTalk] New Tower up With Some Issues 2L40 TH7
>
> Well my 70' Rohn 45 in the air. As is the Orion OR-2800 rotator, (the
> mounting of this rotor is the coolest thing since sliced bread!!!) 21
> foot galvanized HD steel mast, (not water pipe), a 2 element Cushcraft
> 40 meter beam (Older one) and a TH7 that I just went through and
> replaced hardware and the matching section is all new.
>
> Just after the 40 was put up, I checked the match with my MFJ-259B. It
> was resonant at 7.080.
>
> Now the TH7 just went up 9' below the 40. Re-checked the match on the
> 40 and it was not resonant at 7.090. Looks as if the 2 element is
> effected little by the tribander.
>
> Now checked the match on the TH7, I was not so good.
> The TH7 is using the "DX" element lengths.
>
> 20 Meters: flat at 14.090. Climbs to 1.3:1 at 14.000 and up to 2:1 at
> 14.250.
> 15 Meters: 1.2:1 at 21.390 Never lower than that.
> 10 Meters: 1.2:1 at 28.600. above 2.5:1 at 21.100.
>
>
> This is measuring at the end of the jumper hooked onto the balun.
>
> The booms of the 2 antennas are parallel.
>
> Any input would be helpful!
>
> Thanks and 73
> Jim W7RY
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
> "Wireless Weather Stations", and lot's more. Call Toll Free,
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|