Re: Another thought (Re: Emergency Part 15 AM broadcasting)
The center conductor of the Talking House's "F" jack is the 'hot' side, to which the antenna is connected. The barrel of the jack is the ground side, and the counterpoise wire is connected to it. Ocean State Electronics
www.oselectronics.com carries two items that are perfect for this. Their male "F"-to-female BNC adapter (Cat. No. 27-8100, which Radio Shack also sells) and a male BNC-to-binding post adapter (Cat. No. 25-2390) are perfect for this application. You screw these two adapters together and then screw the male "F" end onto the Talking House's "F" jack. You connect a 1/4 wavelength insulated wire to the red binding post (antenna), connect a second one to the black ground (counterpoise) binding post, and you're in business. To bleed off wind-induced static charges, you might want to connect a 5K or 10K (1/2 watt or 1 watt) non-inductive resistor between the red antenna binding post and an 8 foot ground rod (long wire antennas can pick up considerable charge from wind). This will protect the transmitter and prevent static noise.
A 1/4 wavelength (234 divided by your frequency in MHz) at 1600 kHz (1.6 MHz)is 146.25 feet. I use 1600 kHz because many people have older AM radios that won't tune higher than 1600. (The fellow in the article uses a 33' antenna because he's on the 40 meter [7 MHz - 7.3 MHz] ham band, and 1/4 wavelength there is 10 meters or 33 feet.) If your station is well-known in the community, it might be best to stick with the frequency you're on now, so listeners won't have to find you on the AM band.
From what I've read about hams using 160 meter (1800 kHz - 2000 kHz, just above the AM band) wire antennas in trees, the wind-induced wire motion doesn't seem to affect reception very much. Your RangeMaster's ATU is designed to match the very short (at AM band wavelengths) whip antenna. If you just connect a long random wire without a variable capacitor, the ATU's inductor coil plus the wire will make the antenna *WAY* too long (electrically long, that is). The variable capacitor will electrically shorten the antenna to compensate for the inductor. A 365 pF variable capacitor should work fine, and Keith Hammond could recommend the optimum setting to match at various frequencies. -- Jason
> > Simcha, another thought comes to mind. If you have a
> > Talking House
www.talkinghouse.com and
www.actradio.com or
>
> > TalkingSign
www.talkingsign.com Part 15 AM transmitter,
> > these have both a 3 meter wire antenna *and* an RF output
> > jack that is used with special ATUs and CB whip antennas.
>
> > The Talking House has a 75 ohm "F"-Type jack and the
> > TalkingSign has a 50 ohm RCA (Phono) jack.
> >
> > For emergency use, you could cut a 1/4 wavelength wire
> > antenna and a 1/4 wavelength counterpoise and connect
> these
> > directly to the RF output jack on these transmitters.
> Just
> > lay out the counterpoise on the ground and toss the
> antenna
> > up into a tall tree. -- Jason
> >
> Hello thanks for the reply
> I have some questions, reflective of my very shallow
> understanding of broadcast electronics.
>
> For emergency use, you could cut a 1/4 wavelength wire
> > antenna and a 1/4 wavelength counterpoise and connect
> these
> > directly to the RF output jack on these transmitters
>
> In this particular solution are you saying that I should
> insert two wires in the one atu jack of the talking house?
> Would I do that by getting a stereo plug and connecting the
> two wires to it, one for ground and the other for antenna?
>
> How long is a wire of a 1/4 wavelength? In the diagram on
> the site you sent me to it appears to be 33 feet?
>
> On the advice for the rangemaster...you mentioned hooking up
> a longer wire to a bolt etc...can i use the internal atu of
> the rangemaster to tune this wire?
>
> One additonal problem is the trees do the hustle here when
> the wind blows and would that cause the signal to do the
> hustle as well?
>
> Once again thanks for your assistance
>
