06-05-2017, 06:11 PM
If you can come across some Radio Frequency Systems RFS VHF cans with the 4 port box on the side they are really good.
I got 4 of them and they were set for 400KHz offset.
After much experimentation I can now set the offset, the frequencies and the intended slope of the cans.
What I mean is , the cans for the transmit side for a repeater above 147MHZ want a deep notch on the high side and a peak on the low side, while the receive side wants the reverse.
This is all set by the lengths of the coax cable connecting the 4 port box into the top of the notch cavity and the flying lead dangling out of the bottom of the 4 port box.
To widen the offset to 600 KC I lengthened the cable from the can into the box, this I did on all 4 cans and adjusted them for the desired peak and notch frequencies , now to set them for the different peak and null slopes from high side to low side, its just an adjustment of the length of the cable dangling (unterminated) from the lower port on the box.
So, whats in the box ? Lets open it up . Its glued on so some persuasion was required to open the lid.
It consists of 4 N connectors joined up with teflon silverplated coax in a square. The lengths are interesting and i will get around to measuring them so people can replicate them for their own use.
Apparently these things aren't made anymore, so I am hoping the manufacturer wont mind me describing the lengths of whats inside.
Any interest in this? it would appear these can be added onto any old notch cavity and give it the peak and notch as required.
73 Dave jds
I got 4 of them and they were set for 400KHz offset.
After much experimentation I can now set the offset, the frequencies and the intended slope of the cans.
What I mean is , the cans for the transmit side for a repeater above 147MHZ want a deep notch on the high side and a peak on the low side, while the receive side wants the reverse.
This is all set by the lengths of the coax cable connecting the 4 port box into the top of the notch cavity and the flying lead dangling out of the bottom of the 4 port box.
To widen the offset to 600 KC I lengthened the cable from the can into the box, this I did on all 4 cans and adjusted them for the desired peak and notch frequencies , now to set them for the different peak and null slopes from high side to low side, its just an adjustment of the length of the cable dangling (unterminated) from the lower port on the box.
So, whats in the box ? Lets open it up . Its glued on so some persuasion was required to open the lid.
It consists of 4 N connectors joined up with teflon silverplated coax in a square. The lengths are interesting and i will get around to measuring them so people can replicate them for their own use.
Apparently these things aren't made anymore, so I am hoping the manufacturer wont mind me describing the lengths of whats inside.
Any interest in this? it would appear these can be added onto any old notch cavity and give it the peak and notch as required.
73 Dave jds