Home |
Search |
Today's Posts |
#8
|
|||
|
|||
Jack Twilley wrote in message ...
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 "Tam" == t-tammaru Tam writes: Tam Jack, Have you determined that the radio is actually putting out Tam 100W? The light bulb test should give some indication. I have an MFJ Versa Tuner II which has a power meter. It's not laboratory certified, but the needle does go all the way up to 100 when I tune up and transmit. Well, you know the radio works... I can't get the wire any higher than it is right now at this current location. This is pretty much the best I can do, and this little antenna already totally fills my yard and the yards of each of my neighbors (with their permission). It's a multiband fan dipole with three pairs of legs, cut for 40, 20, and 10. Your antenna is *very* efficient on those three bands, unless you have coax or connection problems and power is not making it to the antenna. BTW, the 40 legs will work 15 ok, if you tweak the match with the tuner...Will be pretty efficient on 15 also as a 1.5 wl dipole. My current goal is to acquire a noise bridge and see where the antenna resonates, then trim the antenna as necessary until it resonates in the right places. Good idea. You shouldn't really need the tuner. After that, I'll look into feedline length modifications as necessary. Should be unneeded. If coax length radically varies SWR, you need a 1:1 balun or choke to cut radation from the shield. Hopefully those two approaches will resolve my current issue. Actually, I don't think you have a problem, assuming no coax or connector problems. Does the receive noise level, and signal levels sound fairly normal, or dead? I think the main problem is trying to work locally using ground wave, with an antenna that is poorly suited for that. But, you should usually be able to work 40m in the day, being it's mainly NVIS. 20 miles is a long way for a low horizontal dipole to work locally without the help of skywave. A purely horizontal antenna has no groundwave, if no vertical feedline radiation, etc. It has a space wave, but it's going to be hard to work 20 miles over the noise. If both of you had verticals, it would probably be easy. As far as comparing antennas, all you have to do is use a antenna switch, and see which is best on receive. Operation is reciprical 98.8 % of the time, so a transmit test is unneeded. You should be having no problems working 40m in the day, or even 20m to stateside stuff. 10m local will be very tough, but you should be able to work some skywave. A vertical is much better for 10m local. 20 ft high is high enough to work for medium distance skywave. Maybe not a barnburner, but it should be working for general gov work...I've run many lower than that when camping, and had no problems. If you can't hardly work *anyone*, I would check your connections, and coax , etc. Also, if you use the tuner for now, use the bare minimum inductance to get a usable match. That will help reduce tuner losses, which can climb to 20% or so if too much coil is used. I would eventually tune the antenna up, and dump the tuner. There is no real need for it, unless you go off far from where you normally have it tuned. IE: work some CW when the antenna is tuned for the fone band. MK |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Inverted ground plane antenna: compared with normal GP and low dipole. | Antenna | |||
Mobile Ant L match ? | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
QST Article: An Easy to Build, Dual-Band Collinear Antenna | Antenna |