Diplexer Help Please

[MacombMonitor]

Ok, now it's starting to sink in!

Thanks guys!

 

[bluesman905]

I've been using the Phantom 800Mhz for some time now & it's an impressive little antenna. IMHO

oh btw, I ordered the ASCANC and the 821-896Mhz tuned PHANTOM they should be here today. I'm going to experiment, but I would have to imagine that the PHANTOM tuned for specifically 800mhz band will outperform the ASCANC significantly on that particular band...and monitoring MPSCS and 800mhz digital is alot of what I want to do, so thats the whole reason for this mess

- Joe (kd8bxf)

 

[trooperdude]

Nominal bandwidth;
Low port 120-600MHz 1dB down @ 600MHz
High port 800-900MHz 1dB down @ 800MHz
Crossover @ 700MHz
Insertion loss 0.75dB
Available in 50 or 75 ohms impedance
Connectors customer specified

Tin Lee Electronics Ltd. Toronto Canada www.tinlee.com
Link to page http://www.tinlee.com/Diplexers.htm#Table: Standard models LH7 and Order Information

Once you have sussed it out as I have you may enquire of sales;
Mrs. Sneva Lee, E-mail: sneva@tinlee.com

This is still a work in progress and so far the best lead I have.

What was your $$$ quote on that.

I'm interested in something similar.

 

[SIMON11]

I have no technical knowledge on this subject. But out of interest I bought a passive diplexer and I found it no better than using a bnc tee on the scanner. The instructions with the unit do say though that it may need at least one of the antenna to be powered from a mast amp to boost the signal. I am now thinking of buying a mast amp to try it out.
At the moment I use the bnc tee on the scanner and I can connect either or both antenna as I wish. Some frequencies have a slight benefit others are weaker.

 

[RISC777]

I have no technical knowledge on this subject. But out of interest I bought a passive diplexer and I found it no better than using a bnc tee on the scanner. The instructions with the unit do say though that it may need at least one of the antenna to be powered from a mast amp to boost the signal. I am now thinking of buying a mast amp to try it out.
At the moment I use the bnc tee on the scanner and I can connect either or both antenna as I wish. Some frequencies have a slight benefit others are weaker.

Simon,
Did you look at these? http://www.universal-radio.com/catalog/preamps/0973.html I'd like to know myself if you used those specifically or other (please).

 

[SIMON11]

Simon,
Did you look at these? http://www.universal-radio.com/catalog/preamps/0973.html I'd like to know myself if you used those specifically or other (please).

No mine was a lot cheaper than these and the wires clamp into the mast head box and it has a frequency range of only 45mhz to 860mhz. It would be interesting to know if you get one of these, if it is successfull?

 

[RISC777]

I'm looking at one. If/When I get one in I'll let you know.

 

[joey_corleone82]

Where are you in Michigan? There are so many towers, I can monitor MPSCS on a stock rubber ducky inside my SUV, with the hand-held sitting in a cup holder, down on the floor.

Bill

MacombMonitor....I'd love to know where you are monitoring from to get that kind of performance on MPSCS! I know I've posted about this particular issue in about 3 threads but the situation is this: I am currently only able to receive MPSCS towers if I'm about within 10 miles of the tower, maybe a bit less even. My setup is this:

796d mobile, antenex 800mhz phantom tuned for 824-896mhz, 12ft RG8X coax running from the roof of the car in through the door and into the scanner.

When I'm in sterling hts, shelby, utica, north warren area I get Mt. Clemens tower pretty decent (about 3 bars s meter), and I can get Romeo at around 2 bars ....Detroit 701 at a few bars but it's so choppy it isn't worth it.....northville/flatrock is completely dead.....Warren simulcast comes in very nicely. The problem is ....range and dead spots. I keep hearing stories of people able to pull in any tower within 50 miles, I'd like to know what they are doing and I am not doing seriously. I can't get more than 10 miles here.

For instance, I commute every day to dearborn.... all along the 696 Westbound from Mound to Greenfield....can't get any towers at all ....completely dead..... 701 Detroit maybe but it isn't consistant, drops the control channel all the time, and when it does trunk it is choppy. OK so now I'm in southfield right....no towers, completely dead except again maybe 701 but same issues.....jump on the southfield freeway......no towers.......or maybe take greenfield all the way south.....I mean I'm in the D right... at like 6 mile and greenfield I would think I could get 701.....but still pretty inconsistant choppy audio and / or drops the control channel sporatically.

I'd really like to know how I can get CONSISTANT MPSCS tower coverage wherever I drive. I ordered a Larsen 5db 800Mhz antenna yesterday, the Larsen 800-NMO we'll see how that does. I plan on just detaching the phantom from the NMO mount (oh by the way my mount is an antenex NMO mag mount) and attaching the new one. Maybe it's loss in the connectors they gave me, or the coax? Is my situation normal?

If anybody can help or would like to get together sometime and compare setups I'd really like that. If you'd like to please PM or email me...heck at the very least we can compare our mobile setups!

 

[MacombMonitor]

MacombMonitor....I'd love to know where you are monitoring from to get that kind of performance on MPSCS!

To be honest, there are a few things in my favor. Where I live, I have several towers all around me. I monitor Mt. Clemens, Romeo, and Richmond. Also, in Macomb, there are not a lot of tall buildings. My vehicle is a Saturn VUE, which has all plastic side fenders, and door panels. Most I my driving is in the vicinity of those towers.

If I drove the same route you did, I'm certain I'd have the same problem.

Just to rule out problems with your antenna system, try putting an RS800 rubber ducky directly on the back of your radio, (using a BNC 90 degree adapter), and sit it on the top of your instrument panel with the antenna near the windshield. See how that performs.

Bill

 

[joey_corleone82]

To be honest, there are a few things in my favor. Where I live, I have several towers all around me. I monitor Mt. Clemens, Romeo, and Richmond. Also, in Macomb, there are not a lot of tall buildings. My vehicle is a Saturn VUE, which has all plastic side fenders, and door panels. Most I my driving is in the vicinity of those towers.

If I drove the same route you did, I'm certain I'd have the same problem.

Just to rule out problems with your antenna system, try putting an RS800 rubber ducky directly on the back of your radio, (using a BNC 90 degree adapter), and sit it on the top of your instrument panel with the antenna near the windshield. See how that performs.

Bill

well, it's currently bolted into the dash into a custom metal bracket I had made, and I can't remove it without screwing it up and or tools....but I will try the rubber duck just for kicks

 

[kb2vxa]

Hi again,

I recently moved and was out of the mix for a while so things got a little ahead of me. Here's the end of the story (more or less, less I hope) to bring you all up to date.

"What was your $$$ quote on that."
Troop, you missed it so here it is again, $100 US including shipping from Toronto CA to Point Pleasant NJ.

"But out of interest I bought a passive diplexer and I found it no better than using a bnc tee on the scanner...Some frequencies have a slight benefit others are weaker."
Simon, that's where you contradict yourself. You're experiencing the same problem as I was, see Al's post for an explanation of phase reinforcement and cancellation. Simply put, those stray signals I mentioned are in some cases reinforcing ("benefit") and in others cancelling ("weaker") with the tee and in my case the combiner. If you didn't notice any improvement with the diplexer you weren't paying close attention to signal levels or were using the wrong diplexer.

The end of my story is my problem is solved, signal levels are the same as when each antenna is connected separately and the band(s) monitored by the opposite antenna locked out and ignored. In other words the VHF and UHF bands are monitored with that antenna and 800MHz locked out, conversely 800 monitored on that antenna with VHF/UHF locked out so there can be no confusion on the "wrong" antenna. The windup is the diplexer is working perfectly and overall reception greatly improved.

 

[SIMON11]

Hi again,


"But out of interest I bought a passive diplexer and I found it no better than using a bnc tee on the scanner...Some frequencies have a slight benefit others are weaker."
Simon, that's where you contradict yourself. You're experiencing the same problem as I was, see Al's post for an explanation of phase reinforcement and cancellation. Simply put, those stray signals I mentioned are in some cases reinforcing ("benefit") and in others cancelling ("weaker") with the tee and in my case the combiner. If you didn't notice any improvement with the diplexer you weren't paying close attention to signal levels or were using the wrong diplexer.

To be quite honest I connected the diplexer only for a few minutes. I immediately found on connecting the second antenna that the signal dropped on a couple of frequencies. I didn't go any further. It was only a cheap one that stated for use with any vhf-uhf antenna in it's frequency range. It also stated that it may need one of the antenna signals amplifying.
I did not buy an expensive one in case it didn't work and I had just wasted my money.
There are only a few capacitors and resistors in the whole thing. I take your point and it probably is the wrong diplexer.
I find the bnc tee idea o/k. By using it I can scan all frequencies at the same time. It is only on a few frequencies that there is any loss or interference. If I want to listen to these I just disconnect the relevant antenna and bobs your uncle.
Why bother with major expense? A $100 dollar diplexer in the USA will probably be £100.00 in the UK.

 

[Al42]

There are only a few capacitors and resistors in the whole thing. I take your point and it probably is the wrong diplexer.

Simon, that's a splitter with a fancy label. If you can make a diplexer with resistors and capacitors, I must have missed that day when I got my degree. Capacitors and coils, yes, but not capacitors and resistors.