STARMAN,

Why Use a TV type 300 to 75 Ohm Matching Transformer with
your SWL Antenna and 'portable AM/FM/Shortwave Radio.

May I interject my opinion based on some simple observations
using both SWL/HAM Matching Transformers and the cheap TV
type 300 to 75 Ohm Matching Transformers.

ABOUT - The TV type 300 to 75 Ohm Matching Transformers a

* Easy to Find. {RadioShack, WalMart, Walgreens, Kragens, etc}

* Simple to Use. {How To - Hook-Em-Up is Self-Evident}

* Low Cost. {Under $5}

* Generally Functions well and Operates down to 5 MHz and
well above 30 MHz. (Most of the better quality ones are now
"Marked" for 5 MHz and up.)

* Provides Coverage of 'most' of the International
Shortwave Bands: 60M, 49M, 41M, 31M, 25M, 21M, 19M,
16M, 13M, and 11M. (But not 90M and 75M Bands)

* Plus 'helps' to "Attenuate" Strong AM/MW Signals
that create images in the Shortwave Bands.
{This is an Important Bonus.}

* Allows the 'direct' Connection "Hook-Up" of Low Cost
75 Ohm TV type Coax Cable as an antenna Lead-in-Line.

IMHO: For most/many 'portable' AM/FM/Shortwave Radios
using a TV type 300 to 75 Ohm Matching Transformer is
a very good alternative to a SWL/HAM Matching Transformer.
[ Value and Cost ]

iane ~ RHF
..
..
= = = starman wrote in message
= = = ...
Dave wrote:

So, a matching transformer is all I need? I have pretty much decided to use
300 ohm twinlead along the rood ridge with a 300/75 ohm matching transformer
to connect it to the coax, and more as needed between the coax and radio.
Will that honestly work?

Thanks,

Dave

A 300/50 ohm transformer is the most common type for a shortwave folded
dipole. You can still use 75-ohm coax to the 50-ohm side of the
transformer. There would be a slight impedance mismatch but it's not
that important for a receiving antenna. I do not recommend using a
300/75 TV balun for this purpose because it's designed to operate at
much higher frequencies than shortwave. Remember that you *must* connect
the two wires in the ends of the twinlead together to make a folded
dipole. Otherwise the high impedance side of the matching transformer
(300-ohms) won't be the right value for the antenna. Finally, don't
expect this antenna to be great for all shortwave frequencies and
directions. We discussed why this is so in an earlier exchange.


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