Home |
Search |
Today's Posts |
#31
|
|||
|
|||
Dave wrote:
"starman" wrote in message ... Dave wrote: "starman" wrote in message It sounds like you need a passive preselector rather than an antenna tuner, if your receiver can't handle the strong signals on the antenna. Are you hearing stations outside the bands where they are actually located? Is there a lot of noise from many stations all over the shortwave range. I am picking up a few very weak signals out-of-band, and there is only background noise on the DX setting. The RF choke seems to have done a nice job of cleaning up most of the hash and trash in the background. I would like to enhance the signal I am actually looking for, however. During periods of good propogation I have ocassionally picked up Voice of Korea transmissions aimed at Central and South America, and I would like to load the dice in my favor if I can. I really think you should try a passive preselector. It will reject the strong out of band signals which cause intermodulation products while peaking the weak stations. The choke helps but it also reduces the receivers sensitivity to the signals you want to hear. The preselector does the opposite. I used a preselector with my Sony-2010 and an inverted-L antenna. It worked great. Without the preselector the 2010 would overload and produce a lot of spurious signals throughout the shortwave spectrum. It's pretty easy to build a passive preselector that will cover the range of 3-30 Mhz with two coils. The larger coil will tune the range of about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite cores in the coils for the best selectivity or 'Q'. Of course you'll also need an air variable capacitor like 10-365/pf and a simple rotary switch to select the coils. The circuit is a parallel (tank) design which is connected between the antenna input of the radio and ground, along with the antenna itself. If you're not into building, you can buy a passive preselector at: http://www.grove-ent.com/MFJ1046.html Here's an interesting article on antenna tuners: http://www.nyx.net/~dgrunber/tuner.ssi Hmmm. A tank circuit between the antenna input and ground, to improve reception? I believe you, but I don't understand how it works. Could you enlighten me a little? Does it resonate at the selected frequency (chosen by adjusting the variable cap) and thereby "select" that signal for the input to the radio? (This is all I can figure.) I could do that real easy. I have several variable caps of that general size, and can pick up whatever size inductor I need. I even have the charts and formulas for calculating the appropriate value of inductance, just have to sit down with them. Thanks for the suggestion. PS: Haven't checked out the links yet, but will do so asap. Dave The parallel tuned (tank) circuit causes all frequencies above and below the tuned one, to be shunted to ground while passing the desired frequency range to the radio's antenna input. It makes up for the lack of good preselection in the receivers front-end. This is the main problem when connecting a good antenna to a portable radio. Be sure to use coils with ferrite cores for good selectivity. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Antenna feed wire question | Antenna | |||
Long Wire Antenna Question | Shortwave | |||
Long Wire Antenna Question | Shortwave | |||
Long Wire Antenna Question | Shortwave | |||
Balun | Shortwave |