My newest project to keep me entertained is a small 4 watt portable repeater.
I have the following parts:
UHF HT600
UHF Bendix King LPU handheld
Sinclair MR3332 mini duplexer that's about 6" x 4" in size.
I'm looking for some advice as to where to position the radios in relation to each other and the duplexer. I'm planning on using the Motorola for RX and the King for TX. The King has a large heatsink with a flat spot where the belt clip usually goes. I'm thinking using it for TX since I can bolt that sink to some aluminum for extra heat dissipation.
I want to keep it as small as possible but how close can the radios be?
Should I keep the TX radio from physically touching the duplexer?
Should each radio be separated with some sort of shielding?
I made a similar vhf setup some time back but it was larger than this one will be. I don't want to put a lot of work in it then find out I have to separate things more.
Building a small 4 watt UHF repeater (need const. hints)
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I'd package the radios and battery adapters (I'm assuming you are not running this on individual radio batteries) in individual boxes. the cast aluminum hammond boxes should work. use ferrite beads on all feedthru connections. the boxes can help dissipate heat as well..
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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 4 Watt Portable Repeater
I would provide a minimum of 6 inches separation in between the synthesized portables so the synthesizers don't interfere with each other.
You could place the mini duplexer between the two handhelds.
Use double shielded RG-400/U or equivalent coaxial RF cables to minimize stray RF.
As for the DC power to the radios, you could order piece parts from a /\/\ HT-600 Convertacom for the Battery sleeve, Charger contacts and a voltage regulator and do the same for the Bendix King product. This way the portable repeater package would have it's own battery back up besides the +13.6V DC source you're planning to use.
If you're using a Power Supply, it should be capable of +13.6V DC @ 4~5 Amperes with a heavy duty Zener Diode stud mounted "if" your +13.6V DC source should surge out of control and doing damage to the handheld batteries and other circuitry.
If you decide to mount the handhelds in separate metal enclosures for RF shielding purposes, then use .01uFd Feedthru Capacitors for the Analog Audio and DC Voltage lines. For the RF, I would suggest using chassis mounted SMA connectors.
Keep the UHF External Antenna as far away from the repeater itself to minimize Desense problems. If the /\/\ HT-600 has a tuning coils on its RF Deck, provide access holes on the metal shielded box so you can align the circuit on the bench for minimum Desense and best receiving signal sensitivity while the Bendix King handheld is transmitting.
You could place the mini duplexer between the two handhelds.
Use double shielded RG-400/U or equivalent coaxial RF cables to minimize stray RF.
As for the DC power to the radios, you could order piece parts from a /\/\ HT-600 Convertacom for the Battery sleeve, Charger contacts and a voltage regulator and do the same for the Bendix King product. This way the portable repeater package would have it's own battery back up besides the +13.6V DC source you're planning to use.
If you're using a Power Supply, it should be capable of +13.6V DC @ 4~5 Amperes with a heavy duty Zener Diode stud mounted "if" your +13.6V DC source should surge out of control and doing damage to the handheld batteries and other circuitry.
If you decide to mount the handhelds in separate metal enclosures for RF shielding purposes, then use .01uFd Feedthru Capacitors for the Analog Audio and DC Voltage lines. For the RF, I would suggest using chassis mounted SMA connectors.
Keep the UHF External Antenna as far away from the repeater itself to minimize Desense problems. If the /\/\ HT-600 has a tuning coils on its RF Deck, provide access holes on the metal shielded box so you can align the circuit on the bench for minimum Desense and best receiving signal sensitivity while the Bendix King handheld is transmitting.
Thanks for the tips. I will probably put them on each side of the duplexer. Also, I'm planning on using parts from a portable jump start packs for a power system since they have a decent battery and 110v charging system all inside.
My main problem right now is locating a line that can indicate proper PL decode. I found an audio amp power line but it runs straight from the micro p to the audio chip and the pins are far too small to solder anything.
Is there a way to tap the voltage that goes HI on the speaker audio without destroying the audio quality?
My main problem right now is locating a line that can indicate proper PL decode. I found an audio amp power line but it runs straight from the micro p to the audio chip and the pins are far too small to solder anything.
Is there a way to tap the voltage that goes HI on the speaker audio without destroying the audio quality?
OK, need a few more pointers.
So far the setup works better than expected when tapping the audio from the top of the volume pot where it remains constant. It is routed to a flat audio input to the BK.
I wanted to try the ASTRO repeater setup that some have had some success with. I tapped the discriminator in the HT600 RX radio and routed a line outside to experiment with that. The audio still sounds excellent when the disc. is routed to the BK but the HT600 has trouble decoding PL. I realize that PL is not used with ASTRO but I wanted to get it to work first before moving on to digital.
It seems that tying the HT600 disc. line directly to the flat audio input point of the BK is dragging something down in the 600.
Is there something I should do to match the two better?
So far the setup works better than expected when tapping the audio from the top of the volume pot where it remains constant. It is routed to a flat audio input to the BK.
I wanted to try the ASTRO repeater setup that some have had some success with. I tapped the discriminator in the HT600 RX radio and routed a line outside to experiment with that. The audio still sounds excellent when the disc. is routed to the BK but the HT600 has trouble decoding PL. I realize that PL is not used with ASTRO but I wanted to get it to work first before moving on to digital.
It seems that tying the HT600 disc. line directly to the flat audio input point of the BK is dragging something down in the 600.
Is there something I should do to match the two better?
You might try using something like a high value resistor
in series with the wire you used to tap the audio on the
portable. Many circuits load down the point where you
make the connection. The resistor will help to isolate this
point.
You might try something like a 100K value for the resistor.
Normally the input circuit your feeding the audio into will
have gain to make up for the low level caused by this high
value resistor.
Jim
in series with the wire you used to tap the audio on the
portable. Many circuits load down the point where you
make the connection. The resistor will help to isolate this
point.
You might try something like a 100K value for the resistor.
Normally the input circuit your feeding the audio into will
have gain to make up for the low level caused by this high
value resistor.
Jim
mancow wrote:OK, need a few more pointers.
It seems that tying the HT600 disc. line directly to the flat audio input point of the BK is dragging something down in the 600.
Is there something I should do to match the two better?
I put a .1 cap in the link and that cleared up the problem completely. Apparently the DC is being dragged down too far with a direct connection.
But, will a cap kill any possibility of a digital transmission being passed?
Also, can someone explain what CLIP IN is? Is see a tie in point in the transmit audio amplifier chain of the BK radio with that point available. It goes to a .01 uf cap then on to a series of amplifier stages with no other capacitors in the chain.
What do they mean by CLIP? CLIP what?
But, will a cap kill any possibility of a digital transmission being passed?
Also, can someone explain what CLIP IN is? Is see a tie in point in the transmit audio amplifier chain of the BK radio with that point available. It goes to a .01 uf cap then on to a series of amplifier stages with no other capacitors in the chain.
What do they mean by CLIP? CLIP what?
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jackhackett
- Posts: 1518
- Joined: Tue Jun 10, 2003 8:52 am
I would guess that CLIP IN is an input that passes the signal through a series of amp stages with enough gain to force it to go into clipping, turning whatever signal you put into it into a square wave. Probably for cleaning up a digital signal. Only a guess though, as I'm not familiar with BK radios at all.