I currently have a 40’ antenna for my base unit. My base radio is 50w (44.8 to be expect). If I put another antenna up at the same location and height for one of those small self-contend brief case repeater at what…5w? Will they work together as far as me wanting to TX on the base and the repeater being on the same channel? Or will the base overload the small repeater? Thanks
WRXU693
James
Two things - the repeater is on the same channel? The small retevis style repeaters are not bad. Their filters are not the sharpest, being small, but just remember what they actually do. They allow through the weak signals on the input frequency, and filter out as much of everything else as they can - so if you transmit with 50W (I doubt you meter is really that accurate, to be fair to say 44.8 - 45? Maybe) on thye repeater INPUT - then you are subjecting the receiver - and they are very basic receivers to substantial power. It’s expecting microWatts of energy from a distant portable, and you are shoving 50W up the spout - not good. In practice, the filters are sharp enough that you might be getting 80dB of attenuation once you move a few channels away, so just don’t tranmit on 50W on that frequency, or some channels either side of it. What will happen is that when the repeater fires up, the signals you are listening to on the big antenna will reduce in level because the receiver will be desensitised by the repeaters RF, even though low power, swamping the receiver. Transmitting high power on the channel the repeater is tuned to, is a bad idea.
For info - those repeaters are actually a bit poorly thought through. The filters cannot cope with shofts in frequency, so having them able to do multiple frequencies means that only on the channel the filters were tuned to (and they travel from China really badly if pretuned, by the way) do you get good performance. If you are using say, 166.5625, then 166.550 and 166.575 might just be in the range, but there would be a performance drop. Move further away and it begins to just not work as a repeater, as the receiver starts to receive the output frequency, and the power output drops.
When you mount them - remember the inverse square law. Doubling the distance between them drops the effective power to a quarter - so mounting one above the other can help because of the antenna lobes, and increasing sideways distance can help by reducing the signal level being picked up, however, the two adjustments argue with each other. On commercial towers with excellent filtering, radios work - on very specific frequencies. People have tried to connect unused, but connected old antennas to ‘check receivers’ and discovered they work dreadfully without filtering - every transmission from tower users doing nasty things to a perfectly decent reciever.
Great information. Thank you sir.
WRXU693
That is a cool option.
Is it. But I don’t which unit to pug the mic in on repeater mode with that option turned on. The manual doesn’t say. Do you know?
