Home |
Search |
Today's Posts |
#1
|
|||
|
|||
diversity reception notes
I must be doing something wrong.
Frequency 6.486MHz (BTW arabic male) I first tried 2 active dipoles seperated by 100' on a north to south line. Next I tried a 50' wire 6' off the ground with a WinRadio WR-LWA-0130 "long wire adpator, with either of the active dipoles, then I ran another 50' at right angles for the first, also with a WR-LWA-0130 and tried them all with my Mini Circuits ZFSC-2-1, that while rated for 5~1000MHz operation has been tested and it works fine down to well below 100KHz. The nulls we less frequent but much deeper when they came. I then used a 2nd R2000 and fed each receiver with different antennas and just let the audio "mix" from the respective speaker outputs. The active dipoles gave the best overall effect. There was a very pronounced comb filter effect kind of like The Small Faces "Itchycoo Park" from 1967, or Gobi Grant's "The Westward Wind". Not too bad I think I will investigate some more this weekend. At this point a couple of active dipoles into a broadband "phaser" allow me to peak the signal and that works better the diveristy. Now what would happen if I had 2 sets of active dipoles feeding seperate phasers feeding seperate receivers? I can get at the AGC in my R2000 fairly easily and it should be fairly simple to build a comparator to pass the strongest signal to the audio chain. Just what I need another radio project. Terry |
#2
|
|||
|
|||
diversity reception notes
|
#4
|
|||
|
|||
diversity reception notes
wrote: Hi, I would recommend reading the diversity section of "Communications Receivers: DPS, Software Radios, and Design, 3rd Edition" by Ulrich Rohde, Jerry Whitaker. Generally speaking, mixing the inputs is helpful but not as good as actively switching in the stronger signal. This is somewhat more complex unless you have two receivers. The 2 receivers part is not an issue. The one thing I have more then enough of is receivers. To do this right I will have to tap the AGC off both receivers, feed a comparator and use the comparator to select the strongest signal. This was basicly an attempt to follow up on some comments by D Peter Maus about a "simple" diversity setup he had once that used multiple antennas feeding one receiver. D Peter Maus' discription from another thread: "Each antenna was connected to an RF preamp with a gain of 2-6db. The outputs of the preamps were combined through resistive pads (for isolation) into the RF input of the BC-794. The result was nothing short of amazing, with fading distortions dramatically reduced, and program listening, was quite pleasant. Even my wife was no longer critical of SW listening." My Mini Circuits ZFSC-2-1 has been tested and found to have better then 25dB isolation from 250KHZ to above 30MHz., with less then 3.5dB loss so I could dispense with the preamps. It only "cost" me an couple of hours and I was able to listen during the test. The only time "wasted" was the few minutes spent spooling out my field antennas and pushing a ground rod 4' in the ground. Not the best gorund, but good enough for some quick tests. It is clear the idea has merrit, but it is also clear that to be effective and more then a toy some serious design work will be needed. Since I already have too many projects under way, this one will go in the big dream book of ideas that I hope to pursue when I retire. Terry |
#5
|
|||
|
|||
diversity reception notes
Telamon wrote: For diversity reception you "switch" to the best signal instead of mixing them together. The best approach is two antennas with plus 1 wavelength between them into two separate receivers and switch the audio between them based on a decision circuit looking at both radios AGC voltage. -- Telamon Ventura, California http://www.radioblvd.com/DiversityDD1.html I find the: "At first the engineers speculated that radio waves were being refracted in the ionosphere at different angles and therefore some waves would be intercepted by an antenna while other wave-angles would miss the antenna. A large multiple antenna should capture more wave angles and reduce fading. Actually, they found the opposite happened. Fading became worse with larger antenna arrays. " to agree with my experience in the much shorter active dipoles (~3' per leg) worked much better then the 50' wire antennas. Terry |
#6
|
|||
|
|||
diversity reception notes
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
The "Green" Antenna for AM/MW Radio Reception plus Shortwave Too ! | Shortwave | |||
AM (Medium Wave) Radio Reception - Tips and Links | Shortwave | |||
Automotive Diversity Reception problems- 98 Corvette | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Shortwave |