tone codes and antenna question

[brin831]

ok so here is a couple questions i've done some searching for but not sure of the answer ...

1. is there a specific or best tone code to use with a specific frequency? or is it just a random deal ?

2. in the 450-470 range how close or far apart should two antennas be if they are on the same mast run to duplexers ... does it matter

we have basically built this:

http://www.broadcastsportsinc.com/media ... 20main.jpg

and were wondering about our antenna placement on the same pole as we will have 1 for a repeater on a duplexer combiner and 2 for comms also on duplexer combiners ... all are in repeater pair splits 5 mhz apart.

[Bill_G]

Nice photo though I'm guessing by your description you are not using as many radios. None of those radios have very good rejection. So, you want all the help you can get.

PL tones - mix and match at your pleasure. One caveat - with so many radios in the same band, mounted physically close together, I'd choose different PL & DPL codes for every channel, and may go as far as having different tx/rx codes in the same radio to keep falsing down.

Antenna seperation - Try to get at least 10 feet vertical, or at least 50 feet horizontal (depending on gain and power) between the antennas. Quite honestly, I'd combine all the transmitters into one antenna, and all the rcvrs into another with band pass filters to keep the high side / low side isolated.

[RKG]

Some additional thoughts on tone selection:

1) Obviously, you have to know what tones are used by any co-channel licensees and avoid them.

2) Some folks avoid 3Z (123.0), on the theory that noisy AC-powered devices might cause falsing. I've never observed that phenomenon.

3) Definitely avoid 3B (131.8Hz ) if you have a co-channel who is using any DPL on the input. The DPL turn-off code will false key the 131.8 repeater.

4) The higher the PL tone you select, the greater the potential for hearing some of it through the high-pass audio filter on your receiver.

5) While there are some 500 possible DPL codes, avoid all but the 80 or so that are considered to be least susceptible of falsing. See http://www.midians.com/pdf/tone_signaling.pdf

[Bill_G]

Wow! Thanks RKG. That is one useful pdf. They have just about everything in one place.

[brin831]

yes def. i've been looking for something like that because whoever did our original programing did it just arbitrarily and i'm almost sure they used soem of the ones you said stay away from !!

we are using separate radios for tx and rx then run into a combiner ... 15 watts into a 7 db gain yagi ... each radio is only tasked with one job either tx or rx and yes we can use different codes for each that works.

all of this has to be ina road case in limited space and in a road case so its mobile ... our tx freqs could be as much as 10 mhz away from our rx freqs so do you think we could get away with 5 ft separation of antennas??

[PRR]

we are using separate radios for tx and rx then run into a combiner ... 15 watts into a 7 db gain yagi ... each radio is only tasked with one job either tx or rx and yes we can use different codes for each that works.

all of this has to be ina road case in limited space and in a road case so its mobile ... our tx freqs could be as much as 10 mhz away from our rx freqs so do you think we could get away with 5 ft separation of antennas??

If you're saying that each transmitter's RF output after the combiner network is 15 watts, then feeding a 7dB gain antenna, that's about 78 watts ERP per channel. Even given a 10MHz frequency pair separation (are you actually licensed for that?) you'll need about 85 feet horizontal, or 10 feet vertical separation between TX and RX antennas to prevent desense for about .7uV @ 12dB SINAD in the UHF range. At 5MHz separation, it's almost 600' horizontal and 30' vertical separation. My recommendation is very high Q TX and RX bandpass filters which can get 5MHz pairs down to 20' vertical separation. We've used 80' and 100' manlifts, and the top of the Wilburt mast and the top of the eng van to achieve the necessary vertical separation using similar power levels.

Depending the number of TX channels to be combined and receivers to be fed, and the type of combiner splitter network, the overall systems could be rather large. You may find you'll need two or more equipment racks (say about 20-24 rack spaces each) that you'll have to jumper on site. We barely fit an 8 channel repeater system with 4-wire interfaces into a 24 space, 24" deep rack. As it is, the PSUs are in a second rack and the main rack is too jammed to effectively service in the field easily and quickly.

[brin831]

we are taking the antenna out of one radio into tx side of duplexer, then second radio is on the rx side of duplexer ... 15 watts out of radio into duplexer then 50 ft coax into antenna ...

we are combining tx and rx not tx, to tx

so 1 pair of tx and rx into one antenna

[PRR]

we are taking the antenna out of one radio into tx side of duplexer, then second radio is on the rx side of duplexer ... 15 watts out of radio into duplexer then 50 ft coax into antenna ...

we are combining tx and rx not tx, to tx

so 1 pair of tx and rx into one antenna

Sorry - Misunderstood.

Given this, if you're using band reject/pass duplexers, or if using notch reject duplexers and the two pairs are close enough together so the frequencies each fall within the other duplexer's pass and reject tunings, the RX desense issue is minimal. The concern is now on the TX side such that each could overload the other's final stage or IMD could result from mixing in the finals. Put dual stage isolators between the TX outputs and the duplexer inputs. With this, 5 - 10 horizontal separation should work based upon the separation of the two TX frequencies, though I'd still recommend vertical separation, and with 7dB gain antennas, a half wavelength should be fine (presuming there's about 16' vertical to work with at whatever height the antennas are to be mounted.

[Bill_G]

we are taking the antenna out of one radio into tx side of duplexer, then second radio is on the rx side of duplexer ... 15 watts out of radio into duplexer then 50 ft coax into antenna ...

we are combining tx and rx not tx, to tx

so 1 pair of tx and rx into one antenna

Now I'm confused. In your original post it sounded like you had at least two repeaters - four radios - possibly more as illustrated by the photo, each with their own duplexer and antenna that needed to be considered. Now it sounds like you have just one repeater - two radios - in which case a single duplexer and antenna will get the job done.

[Sikdmax]

Some additional thoughts on tone selection:

1) Obviously, you have to know what tones are used by any co-channel licensees and avoid them.

2) Some folks avoid 3Z (123.0), on the theory that noisy AC-powered devices might cause falsing. I've never observed that phenomenon.

3) Definitely avoid 3B (131.8Hz ) if you have a co-channel who is using any DPL on the input. The DPL turn-off code will false key the 131.8 repeater.

4) The higher the PL tone you select, the greater the potential for hearing some of it through the high-pass audio filter on your receiver.

5) While there are some 500 possible DPL codes, avoid all but the 80 or so that are considered to be least susceptible of falsing. See http://www.midians.com/pdf/tone_signaling.pdf

Just wanted to say thanks for that PDF.... printed it for the binder and saved it for future reference. Thanks!

[brin831]

well yes we have 2 repeaters, xpr 8300

and then also 4 radios ... that may or may not depending upon the situation work as a repeater linked together or for use with simplex opperation ... i would say 9 times out of 10 they would work as repeaters one for tx and one for rx where the com audio, and rx audio would be mixed together and then sent into tx radio.

pairs of radios would be duplexed together, bpbr this would be done for all 4 mobiles like in the picture, so 2 antennas for 2 radios each on a duplexer.

then the repeaters would be the same.

451.35 tx
452.4375 tx
452.75
452.875 tx
452.975 tx
456.35
457.4375
457.875
457.975
463.5
469.4625

as you can see the pairs are listed but rx could be on any of available freqs, we are only lisenced for tx on those set 4, and rest are only licensed at 5 watts or hand held power.

most interested in vertical separation with our setup, based on a quick google search and wave length calculator at 452 is about 26 inches so 10 ft which was mentioned earlier would be about 5 wavelengths?

is that enough, necessary, or recomended.

oh and thanks for everyone's help so much really !!

[PRR]

Presuming you're using fiberglass dipole or colinear designs, 7dB antennas have a significant null directly below the bottom. If height is at a premium (two 7dB fiberglass antennas will be about 14' before separation), a half wavelength should be fine, a little more than 1 foot in the low 450's, but only if using isolators. Without isolators, I'd recommend at least 10', but you may find a bit less works.

Combining the low and high TX frequencies (451.3500 with 452.8750, and 452.4375 with 452.9750) will also help.

[brin831]

well we are using directional yagi antennas so they are not much bigger than a foot or so tall ... yes vertical space is most important as thats what we have ... no real space to go horizontal ... usually ...

any suggestion on isolators?

[PRR]

TX/RX (http://birdtechnologies.thomasnet.com/i ... s?&seo=110);
Telewave (http://www.telewave.com/pricelist/isolators.html); and
EMR (http://emrcorp.com/catalog/78/181/pdf/I ... 0-1000.pdf)
all make very good isolators.

I would also suggest you review some of EMR's application notes and white papers regarding circulators/isolators and the peripheral components required (harmonic filters and sometimes impedance matching networks). http://www.emrcorp.com/techinfo.html

[brin831]

yup gonna have to read through all that in my spare time ?!?

thanks.