[Top] [All Lists]

Re: Topband: Matching Transformer

To: AD5VJ Bob <>, TopBand List <>
Subject: Re: Topband: Matching Transformer
From: Herb Schoenbohm <>
Date: Mon, 29 Dec 2008 19:41:13 -0400
List-post: <">>
AD5VJ Bob wrote:
> "How do you know the transformer is really working, sure your hearing DX you 
> didn't hear before, but is it working like it is
> supposed to."

Some use impedance bridges like the MFJ unit to determine matching 
characteristics and can do so over a large range of frequencies.  But in 
the performance department I use the simple and inexpensive means of 
monitoring AM stations.  This is an easy way to get some general idea on 
Beverages by using AM stations during the day. A station listing is 
available via the website in the Media Bureau section. Keeping a 
log of the signal over noise or just plain S meter readings with 
stations on the front back and sides of the Beverage will give you some 
good ground wave constants for A B checking transformer performance. It 
is a good place to start and also a useful trouble shooting tool 
especially with stations in the 1500 to 1700 Khz range.  I have 
situations were stations to the NW of me in Puerto Rico disappear when 
switching to the reverse port of my DXE two wire Beverage and an 
English  language station in the  Lesser Antilles appears and is just a 
strong as the Spanish station was in the forward direction.  My rule of 
thumb is that good front to back such as this on a Beverage would tend 
to indicate it is working like it should. In some parts of the states 
you can listen to 3 or 4 stations on the same frequency clearly by 
switching around your multiple Beverages.  It is a test I do all the 
time and it has led me to discover all sorts of problems like blown 
termination resistors and even animals eating away the shield of one 
long RG-6 feed run.

Herb Schoenbohm, KV4FZ

Topband mailing list

<Prev in Thread] Current Thread [Next in Thread>