portable 2m repeater patch

[dy2mpl2810]

hi,i want to build a simple low cost portable 2m repeater to be used in our community during disasters and calamities can anyone help me with this project using 2 handheld vhf or a mobile base

 

[betwixt]

Basically, you cross link the audio outputs and audio inputs of the two transceivers. Either the AGC, squelch or CTCSS signals are used to detect an incoming signal and activate the transmitter. The difficult part is preventing the transmitter desensing the receiver. The transceivers must use different frequencies and have filtering in the antennas to prevent the transmission from one reaching the receiver of the other. Commercial and most amateur repeaters use cavity filters in both antennas.

Brian.

 

[pranam77]

@dy2mpl2810
We had used two FT411 handie's from Yeasu where speaker socket of the receiving set was connected to the MIC socket of the transmitting set with 1M pot in between to control the excess audio level entering the TX. Too the antennas what we had used were two different antenna's each for the RX and the TX and both were vertically and horizontally separated by more than a wavelength. It was working fine untill we had a cavity duplexer which is working now.

@betwixt
Is there and simple filter circuits which can be used in place of the duplexer while eliminating the need for separate antenna's?

 

[betwixt]

I don't think anything less selective than a cavity filter will work, especially if the RF power is significant. I have worked with 2m, 1.35GHz and 10.15GHz repeaters like this and no matter how well the antennas are kept apart there is always some coupling. Using cross-band is much easier but when the signals are so close it is very difficult to isolate them. The 2m band here is only 2MHz wide and inside that only about 0.8MHz is allowed for repeaters. Only cavity filters can block high power down to microvolt levels in such a tight bandwidth. The trouble is, at 2m the cavity is huge!

Brian.

 

[dy2mpl2810]

tnx.for the reply i will be very glad if you can supply me with the wiring diagram of what you have done on your handies this will be a great help on my experiment

 

[pranam77]

You'll have to take in to considerations the words from "betwixt". We too had isolation problems when we used the said set up but was worth spending for cavity duplexers at those times where our economical status was not quite good. But at present we have a cavity dup in place. The receiver sensitivity of such set up cannot be guranteed due to blocking of the front end by the tX signals.
The set up is quite simple as explained. Two handies are interconnected with 3.5mm jack on one side (RX )which goes in to the speaker socket and other uses 2.5mm Mono jack which connects the MIC socket of the TX handie. The interconnected centre of the jacks will be connected to a 1M pot to control the audio level fed in to the TX set. You'll practically understand when you see Yeasu FT411.
Good luck
**broken link removed**

 

[dy2mpl2810]

tnx much for the further advice i will try to do as you have said and hope this will work with icom 02n handies berore taking care about the isolation problems

 

[pranam77]

We had done with Yeasu 411 handies and the connections for the speaker and the MIc many differ in Icom-02N. Anyways..best of luck.
Pranam77
**broken link removed**