Building a Repeater
- Thread starter sfd119
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sfd119
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Here's the schmeatic for the BC350A scanner i'd like to use. This is the one without PL/DPLs etc, but that doesn't bother me at this point.
Any one see where I can jumper it?
http://www.studio70productions.com/misc/bc340a.pdf
Any one see where I can jumper it?
http://www.studio70productions.com/misc/bc340a.pdf
In general, a scanner would make for a very poor repeater receiver. There is no selectivity to the front end, and phase noise of the synthesizer is horrendous. That could manifest itself as an incurable level of desense, no matter what duplexer you use, and a receiver that never really fully quiets no matter how strong the signal is.
But I gather that this is essentially a workbench project just to see if you can do it? You're talking about investing in a duplexer. Any idea how much those can cost? This begins to sound like a real project. Fill us in on what you're really trying to accomplish and we can steer you closer to the right direction. A scanner on a high elevation living next to a transmitter, for example, will be maddeningly frustrating, and it will NEVER work good enough for that sort of environment. There's a reason real repeaters are so expensive - cheap hardware simply CAN'T be made to work properly without an inordinate amount of skill.
But I gather that this is essentially a workbench project just to see if you can do it? You're talking about investing in a duplexer. Any idea how much those can cost? This begins to sound like a real project. Fill us in on what you're really trying to accomplish and we can steer you closer to the right direction. A scanner on a high elevation living next to a transmitter, for example, will be maddeningly frustrating, and it will NEVER work good enough for that sort of environment. There's a reason real repeaters are so expensive - cheap hardware simply CAN'T be made to work properly without an inordinate amount of skill.
sfd119
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I'm talking about a cheapy Ebay duplexer.
Anyway, I found the COS lead on the RX Radio (the FT-2400): FT2400 COS Hookup
Now, does anyone know what lead I need to hook this up to for the Mic to TX on the TX Radio (FT-2500M)?
Here's the pinout for the FT-2500M:
PIN1 CALL BUTTON.
PIN2 RX AUDIO.
PIN3 PTT.
PIN4 MIC.
PIN5 GROUND.
PIN6 + 5 VOLTS
PIN7 UP.
PIN8 DOWN.
Anyway, I found the COS lead on the RX Radio (the FT-2400): FT2400 COS Hookup
Now, does anyone know what lead I need to hook this up to for the Mic to TX on the TX Radio (FT-2500M)?
Here's the pinout for the FT-2500M:
PIN1 CALL BUTTON.
PIN2 RX AUDIO.
PIN3 PTT.
PIN4 MIC.
PIN5 GROUND.
PIN6 + 5 VOLTS
PIN7 UP.
PIN8 DOWN.
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Excellent! Couple that with a cheapy receiver, and you have a perfect recipe for failure! =)
Seriously (?), repeaters can be stupidly simple devices, but in order to actually work, the components need to meet some minimum requirements.
Getting a signal out of a receiver to key a transmitter is trivial. Getting it to pass audio is also trivial.
Getting it to do either really well can be a pain in the neck. Good luck.
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do it with what you have as a learning experience, but when you get ready to have a real repeater with good performance you should apply what you learned with this and get better components. i applaud your efforts to learn, and you should keep in mind that the folks saying X wont work are telling you because they already know what you do not yet. once you see how to make it work, then you can go about building a better one you can actually use.
The easiest, cheapest and arguably one of the best ways is to strap a couple of 16 pin options board Motorola Maxtracs together. You don't even need to build an interface. You can simply buy one of these off ebay. Repeater Interface for Motorola Radio Maxtrac New - eBay (item 250706203874 end time Nov-02-10 21:31:35 PDT)
If you are using flat audio out and in it will even pass P25 digital.
If you are using flat audio out and in it will even pass P25 digital.
Repeater
I have built a very basic portable emergency repeater in a 18 inch audio road case. Using two Yaesu 7800's and a box called a "Night Logger". The Night Logger was designed to hook up to the speaker out of a radio/scanner and when it received audio it would pass the audio to a output for mic in on a cassette recorder and also using ground closure start the tape recorder.
The tape recorder start line will trigger the PTT and the line out feeds the Mic in. There are audio setting for the output and input and a delay. Using the delay to set from zero hand time to as long as thirty second of hang.
The two 7800's, power supply and box are on a pull out tray.
So the 7800;s allow any U/V CTCSS/DTCS input and output. Using antenna separation at this time. Using basic unit gain whips on a building gives surprising range.
I have found that I can add a Ramsey DTMF kit and it would allow for some remote control of the unit.
Remember this is only an emergency station and if needed the repeater can be turned off mics attached and you have two base units or a base and a unit for a packet. I don't have any pictures right now but will glade to add some if anyone is interested.
I have built a very basic portable emergency repeater in a 18 inch audio road case. Using two Yaesu 7800's and a box called a "Night Logger". The Night Logger was designed to hook up to the speaker out of a radio/scanner and when it received audio it would pass the audio to a output for mic in on a cassette recorder and also using ground closure start the tape recorder.
The tape recorder start line will trigger the PTT and the line out feeds the Mic in. There are audio setting for the output and input and a delay. Using the delay to set from zero hand time to as long as thirty second of hang.
The two 7800's, power supply and box are on a pull out tray.
So the 7800;s allow any U/V CTCSS/DTCS input and output. Using antenna separation at this time. Using basic unit gain whips on a building gives surprising range.
I have found that I can add a Ramsey DTMF kit and it would allow for some remote control of the unit.
Remember this is only an emergency station and if needed the repeater can be turned off mics attached and you have two base units or a base and a unit for a packet. I don't have any pictures right now but will glade to add some if anyone is interested.
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Does this unit have a variable hand time adjustment or audio gain adjustment? I may have to replace my night logger box with one of these.
n5usr
Member
You would use the PTT connection, but you probably can't direct-connect. You need to know what the COS from the 2400 does. Measure it with a multimeter when receiving / not receiving a signal. Odds are it will have a voltage present during one state, and go to zero in the other. I seriously doubt it will be a simple open-collector transistor (as there would be no point to have that buried inside the radio).
On the other end, the PTT connection expects a switch closure - no voltage at all, just a contact. So you need to use a very small relay (like a reed relay) or transistor switch to emulate that. You would use the COS signal to trigger the relay or transistor.
The problem with relays, is depending on where that COS signal comes from it may not be able to supply enough current to trigger the relay. In which case you would have to use a high-impedance transistor switch circuit to prevent loading it down. Also, relays can generate a feedback voltage spike when the coil voltage is removed, be sure to put a diode across the relay coil so you don't fry something in the 2400! (The diode goes "backwards" across the relay so no current flows through it normally - arrow points to +VDC from the COS line.)
You also need to be sure you supply the right signal - if the COS goes active (voltage) when you are receiving a signal, then you use a normally-open relay contact or a simple transistor switch. They will "close" when signal is present. If the voltage goes the other way - to 0V when signal received - you use normally-closed relay contacts or would need a slightly more complicated transistor switch config to get what you are after. Also realize the simplest ways of reversing the signal (such as the N.C. relay contact) means if your receiver is turned off or dies, your transmitter goes on and stays on!
If you use a repeater controller, you may well not need any of this. They often have circuitry built in to handle this, you'd just wire the COS line to the controller. It would also have timers to unkey the transmitter if it gets stuck on for too long.
I think someone mentioned it before, Repeater Builder is an excellent resource for info on all kinds of repeater-related topics. They may not have an article on exactly the radios you are using, but they may have something related that could help. Interesting to read through in any case.
The Repeater Builder's Technical Information Page™
On the other end, the PTT connection expects a switch closure - no voltage at all, just a contact. So you need to use a very small relay (like a reed relay) or transistor switch to emulate that. You would use the COS signal to trigger the relay or transistor.
The problem with relays, is depending on where that COS signal comes from it may not be able to supply enough current to trigger the relay. In which case you would have to use a high-impedance transistor switch circuit to prevent loading it down. Also, relays can generate a feedback voltage spike when the coil voltage is removed, be sure to put a diode across the relay coil so you don't fry something in the 2400! (The diode goes "backwards" across the relay so no current flows through it normally - arrow points to +VDC from the COS line.)
You also need to be sure you supply the right signal - if the COS goes active (voltage) when you are receiving a signal, then you use a normally-open relay contact or a simple transistor switch. They will "close" when signal is present. If the voltage goes the other way - to 0V when signal received - you use normally-closed relay contacts or would need a slightly more complicated transistor switch config to get what you are after. Also realize the simplest ways of reversing the signal (such as the N.C. relay contact) means if your receiver is turned off or dies, your transmitter goes on and stays on!
If you use a repeater controller, you may well not need any of this. They often have circuitry built in to handle this, you'd just wire the COS line to the controller. It would also have timers to unkey the transmitter if it gets stuck on for too long.
I think someone mentioned it before, Repeater Builder is an excellent resource for info on all kinds of repeater-related topics. They may not have an article on exactly the radios you are using, but they may have something related that could help. Interesting to read through in any case.
The Repeater Builder's Technical Information Page™
sfd119
Member
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- Jul 18, 2009
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I can't direct connect as it will TX when I do that. I did measure it with a multimeter and it gave me ~4.5 volts when squelch was on and 0 when it was off. Regardless of the setting, it always TXs the radio.
knightrider
Member
sfd, go to these links, and read up on some of the things that have been mentioned here so far. I think you are headed in the right direction, and applaud you for trying. It may seem like "re-inventing the wheel", but that sometimes leads to new ideas and inventions.
The Repeater Builder's Technical Information Page™
Amateur Repeater Builders Page
Knightrider...
The Repeater Builder's Technical Information Page™
Amateur Repeater Builders Page
Knightrider...
kpoe_28
Member
No the handover time is not adjustable,It's set to 2 seconds, audio gain can be adjusted by the volume control on the RX radio. By no means does this make a top of the line repeater but for $75 bucks shipped and comes with the cables you need for whichever radio's you plan on using. Got mine from radioshop888.com took about two weeks for it to get here.
Specifications
Power Supply :Build-in 8.4 Lithium-lon battery
Power Consumption :38mA
Charging & External Power : DC 12V
Charging Current :250mA
DTMF Remote Control Functions :Repeat Function ON and OFF
DTMF Remote Control Protection :User define 4-digit Password
Carrier Handover Time :Approx 2 second
Carrier Detect Activation Time :Approx 1/2 second
Indicators :Status LED and External Power Supply input LED
AC Adapter :Input AC 100~240 50/60Hz, Output DC 12V 0.5A
mjthomas59
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- Nov 29, 2006
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- 510
Another Option
I found some great information on repeater-building from this website.
DIY Icom Repeater
I'm really just getting into the whole repeater building, repeater controller, remote access, etc side of this hobby. What i've found through trial and error is that there are a number of easy ways and hard ways which get you to the same place. The easy ways generally cost more money, the hard ways seem to be cheaper in the short run but more expensive in the long run, as you burn up equipment and splice the wrong wires etc etc lol (been there done that) The key though is learning as much as you can along the way.
I'll agree with Mancow on this one, you can buy 2 motorola radios off ebay along with the link cable and you can have full duplex operation, a small amount of control such as hang time and TOT, and it will cost you less than $300 with one of those cheap mobile duplexers.
Example being: GM300 VHF Radios built to Radio Repeater ( 25 watt TX) - eBay (item 270648629582 end time Oct-19-10 12:25:24 PDT)
That seller had a buy it now price on that same system for $175. Add $100 for the duplexer and a little for shipping. You now have something that won't burn up as easy and ultimately could be relied upon in an emergency.
Personally I went along with the directions on that first link I posted. I am already a icom user and like their stuff. 2 brand new Icom F121's ($500 brand new with 2yr warranty), a repeater interface cable from gmrsoutlet.com (48.00), a mobile duplexer ($80), a duracomm power supply($45.00), and CPU fan that I had on hand, and I have what Icom considers a $2000 repeater system... don't believe me here is the link:
ICOM CY121SDP VHF 50W 8CH REPEATER 136-174MHZ W/DUPLEX - eBay (item 130420348295 end time Nov-10-10 12:39:24 PST)
Except i'm using the 128ch mobiles(which help when using as a base station) and Icom builds theres with the cheaper 8ch mobiles. So i'm sitting at less than $700, and even adding the Icom repeater housing to make it look professional is only another $230... so i'm at $930.00.. $825.00 if i used the 8ch radios. The point being I just built something for a fraction of the cost, that gives me almost 100% reliability, and when the power is turned down to 25watts won't overheat even during long duty cycles. This same system could be built using used equipment for closer to $450.00 minus the professional housing.
The only reason I didn't go with the moto's is because they won't do narrowband and I like having warranties.
Either way this is a great hobby and I wish you luck on your adventure into building your own setup. Hopefully that first link gives you a little info and maybe sparks some ideas for you. Good luck!
I found some great information on repeater-building from this website.
DIY Icom Repeater
I'm really just getting into the whole repeater building, repeater controller, remote access, etc side of this hobby. What i've found through trial and error is that there are a number of easy ways and hard ways which get you to the same place. The easy ways generally cost more money, the hard ways seem to be cheaper in the short run but more expensive in the long run, as you burn up equipment and splice the wrong wires etc etc lol (been there done that) The key though is learning as much as you can along the way.
I'll agree with Mancow on this one, you can buy 2 motorola radios off ebay along with the link cable and you can have full duplex operation, a small amount of control such as hang time and TOT, and it will cost you less than $300 with one of those cheap mobile duplexers.
Example being: GM300 VHF Radios built to Radio Repeater ( 25 watt TX) - eBay (item 270648629582 end time Oct-19-10 12:25:24 PDT)
That seller had a buy it now price on that same system for $175. Add $100 for the duplexer and a little for shipping. You now have something that won't burn up as easy and ultimately could be relied upon in an emergency.
Personally I went along with the directions on that first link I posted. I am already a icom user and like their stuff. 2 brand new Icom F121's ($500 brand new with 2yr warranty), a repeater interface cable from gmrsoutlet.com (48.00), a mobile duplexer ($80), a duracomm power supply($45.00), and CPU fan that I had on hand, and I have what Icom considers a $2000 repeater system... don't believe me here is the link:
ICOM CY121SDP VHF 50W 8CH REPEATER 136-174MHZ W/DUPLEX - eBay (item 130420348295 end time Nov-10-10 12:39:24 PST)
Except i'm using the 128ch mobiles(which help when using as a base station) and Icom builds theres with the cheaper 8ch mobiles. So i'm sitting at less than $700, and even adding the Icom repeater housing to make it look professional is only another $230... so i'm at $930.00.. $825.00 if i used the 8ch radios. The point being I just built something for a fraction of the cost, that gives me almost 100% reliability, and when the power is turned down to 25watts won't overheat even during long duty cycles. This same system could be built using used equipment for closer to $450.00 minus the professional housing.
The only reason I didn't go with the moto's is because they won't do narrowband and I like having warranties.
Either way this is a great hobby and I wish you luck on your adventure into building your own setup. Hopefully that first link gives you a little info and maybe sparks some ideas for you. Good luck!
DODGEIT
Member
The duplexers on Ebay are of the mobile type. If you plan on doing a 2 meter frequency then those will not work as the channel separation is not the one used in Ham radio. If you use a UHF frequency pair then they will work. I don't know if they are designed for continuous duty that a repeater demands.
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