Eric, and group.
Amen to Jim's reply about 1.2:1 being quite acceptable, quite good actually,
and in no need of extra effort to reduce....
Take a look at the bottom of the page of the LP 1017 data sheet below, to see
the wide variation of (acceptable) SWRs over its design frequencies.
Granted, one reason to seek extra low SWRs is due to the fold back protection
circuits of ham gear, that sometimes trigger at SWRs far lower than those that
would otherwise do perceptible harm to a signal, or damage a well designed
transmission line system. The LP 1017, while perfectly usable, and I can
attest, puts very good sigs over the pole, and to other DX points,(65' in the
clear with views to the Pacific helps) might present loading problems to some
modern Ham gear, without antenna matchers.
Another consideration.... The BN-86 Balun over the decades shows up in actual
use to have a fairly high failure rate when used at it's limit power ratings.
I have personally had 2 (out of 3) fail in my ham career. There is still a
BN 86 at the end of the boom that I cant get at, to do a post mortem, on the
LP-1017 at N6IJ. When it failed, we built a choke balun from coax, and left
the dead BN-86 where it was at the end of the boom.
There seems to be enough anecdotal evidence/history to suggest that someone
should look at the BN-86 to find if it truly has a design problem, or is
optimistically rated power wise, or if its failures may be due to abuse by
users.. perhaps High SWR can kill it when running High power.
All the best,
Pat Barthelow (916) 315-9271
> From: email@example.com
> To: TowerTalk@contesting.com
> Date: Tue, 8 Apr 2008 12:07:50 -0400
> Subject: [TowerTalk] Any BN-86 Balun Replacement Suggestions?
> TT Gang,
> It looks like my BN-86 Balun used on a TH7-DX beam is giving me grief. The
> antenna was assembled to use the DX or lower portions of the bands. The SWR
> measurements are good on 20 meters, but on 15 and 10 meters the SWR is 1.2:1
> on the CW portion of the band. After doing some basic research and talking
> with a friend we have come to the conclusion the Balun may be causing my SWR
> problems. I am considering a new Balun for as a replacement from DX
> Engineering. DXE have several models to choose from so I will have to wade
> through the details, but several obvious questions come up.
> How do you mount these Baluns on a beam and is the ground strap still
> required for beam mounting or does one 'float' the Balun electrical ground?
> Which DXE Balun model works best on the THY antenna?
> Are there other Baluns I should consider for using with the TH7 antenna?
> Thanks gang,
> Eric - VE3GSI
TowerTalk mailing list