Do duplexers have a dedicated Tx/Rx ?
I am in posession of an old sinclair (7 cavity) mobile duplexer (uhf) that has 4 cavities for transmit and 3 cavities for receive.
Originally the radio it was used for was set up for non-standard split. Transmit=High and Receive=low
Is it possible to use this duplexer in "reverse" or "backwards" in that I can connect transmit to the "RX" port of the duplexer and connect receive to the "Tx" port of the duplexer ?
I'm asking because I would like to convert the radio to a GMRS repeater.
thanks
John
Duplexer dedicated IN/OUT ?
Moderator: Queue Moderator
Just retune the duplexer to match what you need.
I've done it with nothing more than an HT and a Bird wattmeter with a dummy load. But thats the quick and dirty hamsexy way, lol.
I've done it with nothing more than an HT and a Bird wattmeter with a dummy load. But thats the quick and dirty hamsexy way, lol.
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Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
UHF Duplexers
Hello John,
Your 4 / 3 Sinclair Mobile Duplexer from the APCOR Repeater (Am I guessing correctly) was probably constructed in the configuration for a deeper notch, a wider window at -70 dBm rejection for the Rx Input Port on a multi-frequency RCVR / RPTR to Reject the Tx sideband noise and the XMTR / RPTR most likely used the 3 sections for the Tx Input port. I say most mobile Duplexers use 3 by 3 notch type cavities and live with the insertion losses.
Your next question is: Can I flip the input and output? Well if you're not changing the operating frequencies. Say your duplexers are tuned to 468.200 MHz Tx Notch and 463.200 Rx Notch and now you want to Tx on 463.200 MHz and Rx on 468.200 MHz they could be flipped. Just rememeber there might be more insertion on the 4 Filter side than the 3 Filter side.
The most ideal thing to have would be a HP RF Network Analyzer to look at both Notches and the insertion losses. The next best would be a HP RF Spectrum Analyzer with a Tracking Generator. The last would be a Service Monitor with a Spectrum Display and a Tracking Analyzer for tuning Duplexers. All three of these have displays which provide a picture of the notches and insertion losses. And a picture is worth a 1,000 words when you're tuning duplexers.
Dan
Your 4 / 3 Sinclair Mobile Duplexer from the APCOR Repeater (Am I guessing correctly) was probably constructed in the configuration for a deeper notch, a wider window at -70 dBm rejection for the Rx Input Port on a multi-frequency RCVR / RPTR to Reject the Tx sideband noise and the XMTR / RPTR most likely used the 3 sections for the Tx Input port. I say most mobile Duplexers use 3 by 3 notch type cavities and live with the insertion losses.
Your next question is: Can I flip the input and output? Well if you're not changing the operating frequencies. Say your duplexers are tuned to 468.200 MHz Tx Notch and 463.200 Rx Notch and now you want to Tx on 463.200 MHz and Rx on 468.200 MHz they could be flipped. Just rememeber there might be more insertion on the 4 Filter side than the 3 Filter side.
The most ideal thing to have would be a HP RF Network Analyzer to look at both Notches and the insertion losses. The next best would be a HP RF Spectrum Analyzer with a Tracking Generator. The last would be a Service Monitor with a Spectrum Display and a Tracking Analyzer for tuning Duplexers. All three of these have displays which provide a picture of the notches and insertion losses. And a picture is worth a 1,000 words when you're tuning duplexers.
Dan
Ok guys,
Thank you both for the information,
And yes, You guessed correctly------its an apcor and yes I am looking to reverse the splits!
Dan562: what do you mean by there might be more insertion on the four filter side ?
Do you mean more signal (power)? Sorry as I am just learning the whole duplexer thing
Thanks guys--J
Thank you both for the information,
And yes, You guessed correctly------its an apcor and yes I am looking to reverse the splits!
Dan562: what do you mean by there might be more insertion on the four filter side ?
Do you mean more signal (power)? Sorry as I am just learning the whole duplexer thing
Thanks guys--J
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ASTROMODAT
- Posts: 1825
- Joined: Tue Nov 05, 2002 12:32 am
All things being equal, he is pointing out that you have more loss through the 4 filters than 3. The APCOR used 4 filters on the TX side because the UHF MX exhibited a good deal of broadband noise on its TX. Of the 12 or so vendors that responded to the SPs group RFQ for APCOR duplexer filters, only Sinc Labs met all of their specs. That's a darn good duplexer. One other point to keep in mind is the power handling capacity. The APCOR 12 watt unit used the PA from the 40 watt UHF Maxar, and detuned it quite a bit. If you put the TX into the 3 filter RX side, you will inherently have a bit less power handling capacity than did the 4 filter TX side. I believe the 12 watt APCOR was spec'ed at around 18 watts input into the duplexer. I would not run more than 15 watts max into it, since the 3 cans will handle less input power than the 4 can side, and given the fact that you will be using it 100% duty cycle for repeater operations.
Good luck!
larry
Good luck!
larry
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Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
Mobile Duplexers
Essentially what Larry has informed you is correct. Every RF component in that APCOR repeater unit duplexers, RF cables, circulator, low pass fiter all contribute to the insertion losses that will affect the XMTR Power Output and the RCVR sensitivity.
One thing to keep in mind using the MX300 Series radios is to keep the receiver injection level at a minimum, otherwise the repeater's desense level will be much higher and causing degradation in the repeat mode defeating the ability of the repeater's receiver to operate efficeintly.
Since your intentions are to use this APCOR unit as a continous duty 12 watt repeater, you may want to consider some type of a muffin fan to pull the heat out of the unit preventing the MX or Power Amplifier from burning up.
Dan
One thing to keep in mind using the MX300 Series radios is to keep the receiver injection level at a minimum, otherwise the repeater's desense level will be much higher and causing degradation in the repeat mode defeating the ability of the repeater's receiver to operate efficeintly.
Since your intentions are to use this APCOR unit as a continous duty 12 watt repeater, you may want to consider some type of a muffin fan to pull the heat out of the unit preventing the MX or Power Amplifier from burning up.
Dan
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ASTROMODAT
- Posts: 1825
- Joined: Tue Nov 05, 2002 12:32 am
John, I thought you were going to use the APCOR duplexers with another radio to serve as a Ham repeater. If you are going to use the APCOR as a Ham repeater, then that changes things a bit.
First off, I would absolutely use the 4 cavity side for the TX filtering, since the UHF MX broadband noise is significant enough that you really need to! I had spoken with the fellow in the SP group (Bill W?, who since passed away, but whose son still works in the Ft Lauderdale SP Group) who was one of the original lead engineers on this project many years ago, as I had converted some APCORs for Ham use. We initially used these APCORs for helicopter EMS ops for a short time. Later, we used them for full duplex autopatch mobiles in connection with the full duplex MRTI on a Micor repeater. We even had the APCOR SP kit that added a cycolac keypad and internal DTMF generator for DTMF encoding to the front panel of the APCOR.
The Motorola SP group recommended that I consult with Sinc Labs (the manufacturer of the APCOR duplexer) concerning a duplexer re-tune (e.g., UHF MED channels to Ham UHF frequencies). We had to slide them down from the 458 MHz MED channels to our 442 MHz Ham repeater. We sent the duplexers to Sinc Labs up in Canada because there were hardware change out issues, I think involving some capacitors inside of the duplexers, as well as fitting them with different length inter-can cables. Again, because of the high MX sideband noise, Sinc Labs recommended that they make these duplexer h/w changes to ensure proper duplexer performance with such a large frequency shift. Sinc Labs advised me that a simple re-tune attempt would likely be inadequate to support full performance specs with such a large change in operating frequency. Sinc Labs made their h/w changes and did a re-tune on their network analyzer, and all was well. I think it was a bit pricey, though, and they were extremely reluctant to do it (wasn't worth their time to screw with it, but I finally convinced them. I think I had 5 or 6 units redone.)
If you have access to a network analyzer (which we did not at the time), you may be able to experiment and try it yourself. Without a component change or without a cable length rebuild, it is very questionable whether you can achieve adequate performance. If you decide to make this attempt, you will want to check the duplexer specs in the APCOR detailed service manual so you are sure that you are obtaining adequate minimum duplexer performance after your re-tune. Keep in mind that this duplexer was a custom 7 cavity filter made exclusively for Motorola for use in their APCORs, and in their full duplex EMS Micor). As such, you should not assume that it is like some of the typical Ham duplexers that can be tuned over a broad frequency range without any duplexer cable or component changes. This custom (read that “pricey”) duplexer is one reason that the 12 watt APCOR cost $14,500 new. Given that was a 1980 price, if you adjust that for inflation, it would be something like $20,000 today.
Secondly, I wouldn't worry about any need for a PA cooling fan. I understand that you are going to use the stock 12 watt APCOR set-up. I had keyed down for over an hour with my APCORs in testing the batteries (rated at 1 hour key down on a full charge at 12 watts output), and the PA heat sink was barely warm to the touch after 1 hour key down. I believe the MX's Exciter output (about 20 mW) is the input to the PA, so you don't have to worry about overheating the MX. After all, given the amount of traffic on today's Ham repeaters, I doubt you will hardly ever see even a 1 hour talk cycle on your repeater, so the stock set-up should be just fine. As to 1 hour key down, the 12 watt APCOR was spec’ed for this sort of long key down duty cycle for duplex/multiplex operations, so this should not be a problem. And, a fan draws power and is another source of noise. If you ever decide to run the APCOR repeater on its internal battery for AC fail ops, and the like (maybe solar cells?), then even a thermally triggered fan is a power hog that you just don't need. In the highly unlikely event that you ever blow the PA, don't forget that there are tons of those things on eBay for literally nothing. We just threw away 10 of our old 12 watt APCORs, as I had them on eBay for $200 for the entire lot (with new batteries, and many brand new Motorola APCOR chargers), and we got no bites (even with the SP DTMF kits, and they were in 10 of 10 shape, etc.).
Good luck.
larry
First off, I would absolutely use the 4 cavity side for the TX filtering, since the UHF MX broadband noise is significant enough that you really need to! I had spoken with the fellow in the SP group (Bill W?, who since passed away, but whose son still works in the Ft Lauderdale SP Group) who was one of the original lead engineers on this project many years ago, as I had converted some APCORs for Ham use. We initially used these APCORs for helicopter EMS ops for a short time. Later, we used them for full duplex autopatch mobiles in connection with the full duplex MRTI on a Micor repeater. We even had the APCOR SP kit that added a cycolac keypad and internal DTMF generator for DTMF encoding to the front panel of the APCOR.
The Motorola SP group recommended that I consult with Sinc Labs (the manufacturer of the APCOR duplexer) concerning a duplexer re-tune (e.g., UHF MED channels to Ham UHF frequencies). We had to slide them down from the 458 MHz MED channels to our 442 MHz Ham repeater. We sent the duplexers to Sinc Labs up in Canada because there were hardware change out issues, I think involving some capacitors inside of the duplexers, as well as fitting them with different length inter-can cables. Again, because of the high MX sideband noise, Sinc Labs recommended that they make these duplexer h/w changes to ensure proper duplexer performance with such a large frequency shift. Sinc Labs advised me that a simple re-tune attempt would likely be inadequate to support full performance specs with such a large change in operating frequency. Sinc Labs made their h/w changes and did a re-tune on their network analyzer, and all was well. I think it was a bit pricey, though, and they were extremely reluctant to do it (wasn't worth their time to screw with it, but I finally convinced them. I think I had 5 or 6 units redone.)
If you have access to a network analyzer (which we did not at the time), you may be able to experiment and try it yourself. Without a component change or without a cable length rebuild, it is very questionable whether you can achieve adequate performance. If you decide to make this attempt, you will want to check the duplexer specs in the APCOR detailed service manual so you are sure that you are obtaining adequate minimum duplexer performance after your re-tune. Keep in mind that this duplexer was a custom 7 cavity filter made exclusively for Motorola for use in their APCORs, and in their full duplex EMS Micor). As such, you should not assume that it is like some of the typical Ham duplexers that can be tuned over a broad frequency range without any duplexer cable or component changes. This custom (read that “pricey”) duplexer is one reason that the 12 watt APCOR cost $14,500 new. Given that was a 1980 price, if you adjust that for inflation, it would be something like $20,000 today.
Secondly, I wouldn't worry about any need for a PA cooling fan. I understand that you are going to use the stock 12 watt APCOR set-up. I had keyed down for over an hour with my APCORs in testing the batteries (rated at 1 hour key down on a full charge at 12 watts output), and the PA heat sink was barely warm to the touch after 1 hour key down. I believe the MX's Exciter output (about 20 mW) is the input to the PA, so you don't have to worry about overheating the MX. After all, given the amount of traffic on today's Ham repeaters, I doubt you will hardly ever see even a 1 hour talk cycle on your repeater, so the stock set-up should be just fine. As to 1 hour key down, the 12 watt APCOR was spec’ed for this sort of long key down duty cycle for duplex/multiplex operations, so this should not be a problem. And, a fan draws power and is another source of noise. If you ever decide to run the APCOR repeater on its internal battery for AC fail ops, and the like (maybe solar cells?), then even a thermally triggered fan is a power hog that you just don't need. In the highly unlikely event that you ever blow the PA, don't forget that there are tons of those things on eBay for literally nothing. We just threw away 10 of our old 12 watt APCORs, as I had them on eBay for $200 for the entire lot (with new batteries, and many brand new Motorola APCOR chargers), and we got no bites (even with the SP DTMF kits, and they were in 10 of 10 shape, etc.).
Good luck.
larry
Larry and Dan,
Wow,
Thank you for the intense information, This is exactly the kind of stuff I'm looking for, as I am absolutely HELLBENT on using my apcor as a repeater, even if just to meet the challenge.
I was fortunate enough to get the service manual with it so I have been studying it quite a bit.
Its hard to believe nobody grabbed a chance to get these things on ebay, I have been searching for a high power for some time for a good price- and I finally got one complete with manual and charger ($10.00 + shipping!)
Larry, mine is (or was) an SP version as you described with the DTMF pad on the handle but I refurbed it with a brand new housing and didn't want to drill holes in it to re-install the pad so I simply "undid" pad/encoded circuit. When I first became a medic we were still using apcors but primarily low powers with the micor (I think) channel steering encoders (they never worked well) And we did have high powers also -- I was trying to get my employer to give me one thats still sitting in storage but he wouldn't -- probably worried about some legality.
I have been testing (playing) with our portables at work that are set up on low power for use through our GM300 mobile repeaters to see if it worked, and after I jumpered two of the connection points on the receive shield to enable csq. repeat, I'm happy to say it works - or- at least it's repeating, at what power out I don't yet know. and the heatsink gets just warm to the touch after a while.
Well I'm going to re-read and digest all the posts and read the manual again for the specs.
I truely appreciate all of you experience and knowledge on these apcors, If you think of anything else please send the info my way!
Thanks again--John
Wow,
Thank you for the intense information, This is exactly the kind of stuff I'm looking for, as I am absolutely HELLBENT on using my apcor as a repeater, even if just to meet the challenge.
I was fortunate enough to get the service manual with it so I have been studying it quite a bit.
Its hard to believe nobody grabbed a chance to get these things on ebay, I have been searching for a high power for some time for a good price- and I finally got one complete with manual and charger ($10.00 + shipping!)
Larry, mine is (or was) an SP version as you described with the DTMF pad on the handle but I refurbed it with a brand new housing and didn't want to drill holes in it to re-install the pad so I simply "undid" pad/encoded circuit. When I first became a medic we were still using apcors but primarily low powers with the micor (I think) channel steering encoders (they never worked well) And we did have high powers also -- I was trying to get my employer to give me one thats still sitting in storage but he wouldn't -- probably worried about some legality.
I have been testing (playing) with our portables at work that are set up on low power for use through our GM300 mobile repeaters to see if it worked, and after I jumpered two of the connection points on the receive shield to enable csq. repeat, I'm happy to say it works - or- at least it's repeating, at what power out I don't yet know. and the heatsink gets just warm to the touch after a while.
Well I'm going to re-read and digest all the posts and read the manual again for the specs.
I truely appreciate all of you experience and knowledge on these apcors, If you think of anything else please send the info my way!
Thanks again--John