[TowerTalk] Which Balun with the TH7DXX

[Jim Thomson]

Date: Tue, 23 Jul 2013 18:23:45 +0200
From: "Peter Voelpel" <dj7ww at t-online.de>
To: <towertalk at contesting.com>
Subject: Re: [TowerTalk] Which Balun with the TH7DXX

Jim, did you ever try that as a balun on the feed point of a yagi with the
power level RG393 is good for?

73
Peter

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Jim
Thomson

##  17 inches of type 77  1.025 inch OD beads slid over 393 coax = 68 uh. 

Jim   VE7RF

## No.  That is my old F-12   Model B2 balun....which they rate at 25 kw ! 
It comes with a type N connector.   I hate Type N connectors  so would
not trust it.  I used an inter series  adaptor  to get from  Type N  male to UHF female,
and stuffed that into the balun.... just so I could use it as a low power balun. 

##  all  my uh readings were done on my B+K  875B  digital LCR meter... which
takes the readings  at 1 khz.... not RF freqs.  

## Others have stuffed 10 kw pep into a B2..and never blew it up, but I would not 
trust a Type N myself for QRO+. 

##  Moot point these days..as Fair rite no longer makes type 77.  It has been replaced by 
type 31.   They still make type 75 though....but that stuff peaks at 1 mhz for max Z...
and type 77  was very similar..peaking around 1 mhz.  Then it drops off above that.

##  The Z of type 31 beads peaks at 250 mhz....and type 43 beads peaks at 400 mhz.
Type 75 + 77 peaks at 1 mhz.    It sure would be nice is  fair rite could come up with a mix 
that has  a Z peak at   30-50 mhz.  Then WAY less ferrite would be required. 

Jim  VE7RF