RSHAPIRO@BBNA.ARPA (09/10/84)
From: Richard Shapiro <RSHAPIRO@BBNA.ARPA> I would like to stick an antenna tuner of some kind between a long-wire and a SW receiver. Can anyone recommend any models or give me general info on what features/functionality to look for? Many thanks -- Richard Shapiro -------
WMartin@SIMTEL20.ARPA (09/10/84)
From: William G. Martin <WMartin@SIMTEL20.ARPA> I have an old (bought in the 60's) antenna tuner called a "Joymatch"; it is British-made, and was sold both by itself and in a package with a limited-space antenna called a "Joystick", which was some sort of non-conductive rod wound with wire in some special pattern. This tuner was also supposed to work with random longwires; however it is not very effctive, as far as I can determine. It seems much easier to get a sharp null than any sort of peak, when adjusting the controls and watching an S-meter. I can get an S-unit or two higher reading with the tuner in the antenna circuit, but it doesn't seem to be peaking it to an exact frequency. The controls on this are a switch, which switches between taps on a coil, and two variable capacitors. Changing the switch position from one end of the range to the other (it is marked for the various HF ham bands) will cause a noticeable deflection in the S-meter, but changing it just one position has little, if any, effect. Adjusting the capacitors will usually reveal one position where the S-meter DROPS sharply, but any other setting is about the same. I wonder if the effect is nothing more than changing the effective electrical length of the longwire by the amount of wire in the coil? I wonder if anyone else on the list could contribute comments on their experience with receive-only antenna tuners on longwires; do they usually act better than this? This model may be a dud, for all I know. I also have a KS tunable preselector in this antenna circuit (after the tuner); it seems to work quite well, and can raise a signal 4 or 5 S-units or more, and can be peaked to a desired frequency with adjustable gain. Something like that may be of more use than an antenna tuner, if they (as a general rule) don't work any better than the one I've described. By the way, I've used the antenna tuner on various radios -- from a multi-band Allied portable (antenna was a chunk of copper wire run out to the gutters on the BOQ I lived in in Nam) to the presently-used Galaxy R-530, with a ~70' longwire with 30' of lead-in. Its performance has been about the same, though the radios' performance varied substantially. Regards, Will Martin ARPA/MILNET: wmartin@almsa-1.ARPA USENET: seismo!brl-bmd!wmartin -------