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So for reference; I just got done tuning up our portable repeater's duplexer for a campout next week with the local GMRS crew - this is a Celwave 633-6A-2N mobile duplexer, measurement device is an Anritsu MT8212B. This is measured through a couple extra fittings that are part of the normal install; so this adds a few tenths of a dB for insertion loss. For 462.700 Mhz (TX side) - insertion loss is -1.52dB, with a high notch (nothing RX) at -81.72dB For 467.700 Mhz (RX side) - insertion loss is -1.25dB, with a low notch (notching TX) at -87.97dB Below are comparative measurements I took a while ago of a similar Celwave unit (left) vs. the chinesium Jesai/Fumei unit (right); you can see the difference - the cheap stuff is unfortunately garbage at the 5mhz split:

I have tested several of my 70cm ham antennas on my GMRS and the SWR looks fine on all of them. Under 2:1 in all cases and usually about 1.5 which is just fine. Most of them are dual band 2m/70cm. Many of the ham antennas are dual band so this gives you a lot to choose from. Since 465MHz is a shorter wavelength than the ham 70cm you probably could trim the antenna down very slightly to improve SWR but you'd want to be very careful and use a very short coax with a good SWR meter for your testing. I do not see the need for this. You only lose about 10% of your power or .5dB with a 2:1 SWR. There is a huge selection of 70cm ham antennas so it really is a nice option to have. Vince

Gee, I'm a little confused here Miichael. When I tune to a repeater I thought my receiver was set to the output of the repeater rather than the repeater input frequency. Is it different in your radio?

A scanner antenna can be thought of as a jack-of-all-trades, master-of-none antenna. This means the antenna, by design, prioritizes utility on many frequencies over optimum performance on any frequency. Since a scanner may have only one antenna input yet it can scan a wide range of frequencies, the ideal scanner antenna can be thought of as one which provides equal performance over a wide frequency range. Yes, a scanner antenna can be used for transmit, just as any piece of wire can be used for transmit. How well it works, and how long you radio will last using it is purely a function of the antenna’s electrical and radiation characteristics on the frequency in question. If the SWR it presents to the transmitter is within acceptable range for the transmitter, you are good to go. The simplest and most foundational of all antennas is the dipole antenna. Such an antenna resonates quite optimally at one frequency and thus performs exceptionally on it. Near that frequency it does OK to, but its performance degrades commensurate with the difference in frequency from its resonant value. The range of frequencies in which the antenna presents a certain range electrical characteristics to the radio that is deemed acceptable is referred to as its bandwidth. For example, my commercial GMRS antenna as a bandwidth of 10MHz and it only performs well in that range. If you measure the performance of any antenna over a wide range of frequencies you will see an electrical pattern that mimics a mountain range. The wider the range measured the more mountains (variation) you will see. And each design variation will exhibit different patterns of peaks and valleys. Designing antennas to work over a wide range is a major exercise in compromise. Sacrifice this to get that. That will include cases where some frequencies, even ones near one another perform quite differently, most notably in specialized antennas. A scanner antenna is a specialty antenna. Hope this helps. Michael WRHS965 KE8PLM