Batboard

Hello,

Many years ago our local fire department used Remote RF Links to connect a Tone Remote handset to our repeater site. The units we used were called Motorola Handie Talkie, they operated on the UHF band and had different TX and PX frequencies, They are 1 watt transmitters and use crystals. I have included some pictures below to show you what they look like.

My question is this. I have about 6 of them that use the same TX / RX Pairs, I was wondering if it was possible to swap the TX / RX crystals in one of the units so that I can get two to talk to each other, as we no longer have the base unit that was receiving the signal at the tower site.

I don't have too much information on these uints, so any info / insight would be great.

My goal with these is to set up a new RF link to once again use a Tone Remote from our Fire Station to the repeater site using these.

The last picture is the back of the main board of the radio.

More than likely these are wide band radios and can no longer be used on most public safety frequencies. I say this because crystal controlled radios were made many moons ago and are probably not able to be narrow banded.

With the vast availability of newer radios that are narrow banded, you would be much better off using a radio that you can at least be able to maintain and have replacement parts available for. Tone remote controlling radios these days is a simple matter of just using a tone remote adapter and wiring it to the radio. You will need a service monitor to adjust the transmitter audio levels (deviation) to work within the FCC requirements today.

Jim

Jim202 wrote:More than likely these are wide band radios and can no longer be used on most public safety frequencies. I say this because crystal controlled radios were made many moons ago and are probably not able to be narrow banded.

With the vast availability of newer radios that are narrow banded, you would be much better off using a radio that you can at least be able to maintain and have replacement parts available for. Tone remote controlling radios these days is a simple matter of just using a tone remote adapter and wiring it to the radio. You will need a service monitor to adjust the transmitter audio levels (deviation) to work within the FCC requirements today.

Jim

I probably should have mentioned that this will be used in Canada, not the US, so we don't have the same laws and don't need to Narrowband. The repeater site is about 1/2 a mile from our station, we need some sort of RF link to connect the two sites. These Handie Talkie's were made to link two remote sites using Tone Remote.

My main question was if it was possible to swat the TX / RX crystals.

No, you cannot simply swap the crystals.

That model is based on the HT90/HT440 series portable. Manuals for them are as common as chicken teeth these days, but you may be able to find an HT90/440 manual someplace. That said, these things were generally sold as pairs that talked directly to each other acting like a phone line connection between two points. Sometimes they were simplex where the tx freq equaled the rx freq at both ends, but most of the time they were duplex with radio 1 TX= radio 2 RX, and vice versa.

ie: radio 1 tx = 465.000 = radio 2 rx, and radio 1 rx = 460.000 = radio 2 tx

With duplexer cavities to the antenna, you got full duplex audio operation. And if you configured them to stay keyed all the time, they acted like a full duplex four wire phone line. They could run like that for years.

So, you may already have what you're looking for, and just haven't matched up the correct pairs yet.

If i recall correctly these rf link boards are based on the HT440 boards and no you can not swap the rx and tx crystals and make it work that way. The rx and tx crystals must be ordered by a crystal supply manufacture like icm

Bill_G wrote:No, you cannot simply swap the crystals.

That model is based on the HT90/HT440 series portable. Manuals for them are as common as chicken teeth these days, but you may be able to find an HT90/440 manual someplace. That said, these things were generally sold as pairs that talked directly to each other acting like a phone line connection between two points. Sometimes they were simplex where the tx freq equaled the rx freq at both ends, but most of the time they were duplex with radio 1 TX= radio 2 RX, and vice versa.

ie: radio 1 tx = 465.000 = radio 2 rx, and radio 1 rx = 460.000 = radio 2 tx

With duplexer cavities to the antenna, you got full duplex audio operation. And if you configured them to stay keyed all the time, they acted like a full duplex four wire phone line. They could run like that for years.

So, you may already have what you're looking for, and just haven't matched up the correct pairs yet.

I've opened them all up, and all the units are the same.. they all TX on 458.3125 and RX on 453.3125 Each of these units were installed in different buildings in town, Police Department, Fire Department, Public Works, and so on. Those items were collected, but the one at the Repeater site somehow disappeared!!

The Service Manual number for them is 6881040C15 but they are NLA these days as far as i know.

madfrenchie wrote: I've opened them all up, and all the units are the same.. they all TX on 458.3125 and RX on 453.3125 Each of these units were installed in different buildings in town, Police Department, Fire Department, Public Works, and so on. Those items were collected, but the one at the Repeater site somehow disappeared!!

Then, all you need is a decent quality modern programmable mobile set up on the reverse split. ie: tx 453.3125, rx 458.3125. You'll have to figure out the PL/DPL. It may be printed on the module plugged into the daughter board soldered to the main board. In the last photo above showing the circuit board out of the case, look at the metal cased module north of the yellow coil. On the right end, near to the brown ceramic module, should be a printed label telling the PL or DPL.

Bill_G wrote:

madfrenchie wrote: I've opened them all up, and all the units are the same.. they all TX on 458.3125 and RX on 453.3125 Each of these units were installed in different buildings in town, Police Department, Fire Department, Public Works, and so on. Those items were collected, but the one at the Repeater site somehow disappeared!!

Then, all you need is a decent quality modern programmable mobile set up on the reverse split. ie: tx 453.3125, rx 458.3125. You'll have to figure out the PL/DPL. It may be printed on the module plugged into the daughter board soldered to the main board. In the last photo above showing the circuit board out of the case, look at the metal cased module north of the yellow coil. On the right end, near to the brown ceramic module, should be a printed label telling the PL or DPL.

Yeah, the PL tone is actually printed on the front of the unit, 7A 192.8 I was hoping it was an easy conversion so i could use the same hardware.

Thank you for your input!

Well, it will be relatively easy to accomplish with just about anything out there these days.

Something's missing in all of this - forgive me for asking the following three questions:
Why were these RF link units taken out of service?
What is the fire station (and other buildings) currently using to access the repeater?
If these units were at the various buildings and were operated by tone remotes, why would there necessarily be one at the repeater site? Since these are TX/RX units, they would likely be able to access the repeater just like any base or mobile (assuming the repeater was on the opposite frequencies).

First thing I would check is the frequency pair the repeater uses. If they are opposite of these units that would be a confirmation of sorts.
While it's not unknown to use a short range RF link to operate a repeater in a different band, most municipal systems would have either a direct (audio pair for tone remotes) connection, or use repeater access base stations.

Also, for these units to be able to talk directly to each other, they would have to TX and RX on the same frequency (simplex). Using a simplex link to operate a repeater is problematic, but not impossible. Of course, if the repeater used the opposite pair then everything would be through it and you'd hear every other station.

As far as narrow-banding goes - check your current IC license.
If somehow the UHF pair was still licensed for wideband use you might be able to reuse them. If the license has lapsed, any new UHF frequencies assigned would be narrowband only, something these units are not capable of being (re-)used for.

I can answer #3 - these links are used in lieu of phones lines so tone remotes can connect to the wireline card on a repeater. If set for 4W full duplex, dispatch consoles can hear inbound traffic even as they transmit. They are on a separate freq pair from the repeater, and do not participate as a subscriber on the primary system, but more like a crosspatch.

madfrenchie -

I think I have copies of the manuals, if you would like me to pdf them & send them. Give me a couple days to look.

madfrenchie - if you need another of these i may still have one in storage although it is
probably crystaled up in the 460/465 Mhz spectrum and in an outdoor weather resistant
metal box.

Bill_G wrote:I can answer #3 - these links are used in lieu of phones lines so tone remotes can connect to the wireline card on a repeater. If set for 4W full duplex, dispatch consoles can hear inbound traffic even as they transmit. They are on a separate freq pair from the repeater, and do not participate as a subscriber on the primary system, but more like a crosspatch.

Exactly, They were used to extend a tone remote system, the unit at the repeater site connected to a tone remote controller which was interfaced to the repeater. The repeater is VHF.

kb4mdz wrote:madfrenchie -

I think I have copies of the manuals, if you would like me to pdf them & send them. Give me a couple days to look.

I would appreciate a copy of the manuals. Thank you very much!!

madfrenchie wrote:mentioned that this will be used in Canada, not the US, so we don't have the same laws and don't need to Narrowband.

You are correct that Industry Canada is not typically (but not always) forcing narrowband on existing systems, but all new assignments must be narrowband.

The other issue is Industry Canada channel plan does not allow for point-to-point links in 450-470. They will assign in the 403-430 band or possibly even a 900 pair.

I would process your license applications first then see what band/mode of emissions you need, they obtain compatible equipment.