Really? A review for a telescopic? Yes - mainly because of the 5/8 wave adjustment..
The Diamond RH789 (bnc) and SRH789 (sma) is a lightweight, good looking telescopic that can be folded at the base if necessary. It is 8 inches collapsed and 31.5 inches fully extended.
For 95-300 mhz, you adjust it to a quarter wave. For 300-1100 mhz, the adjustment is made to being a 5/8 wave. There is a black and silver sticker/chart on the bottom element in centimeters to guide you.
The bottom 8 inch section is black, as well as the bnc / sma connector. The telescoping elements are somewhat dull brushed-aluminum looking. This is a good thing! If the typical RS shiny-chrome "Adam 12" looking telescopic with loading coil puts you off, the Diamond may command a little more respect.
The use of 5/8 wave for above 300 mhz is interesting - there doesn't seem to be any sort of matching device for 5/8 use. Perhaps it isn't really necessary here, since we're not going to encounter much of any sort of swr loss going essentially from the antenna direct to the circuit board. 5/8 wave antennas usually have about 120 ohms resistive impedance with a large capacitive reactance that gets tuned out, but I can see why for a direct-connect whip to a scanner this may not be necessary - although purists will want a matching device.
The intent here is not to turn this into a 5/8 wave antenna thread. Tuning it to a 5/8 above 300 mhz does work.
For example, when the 789 is telescoped out to about 10.25 inches, it works much better than the canonical RH-77CA duck on 800 mhz. The 77 is not "optimized" for 800 mhz, so it is no wonder that a 5/8 wave non-impedance matched whip works better.
For that test, I used a RS Pro-106 with extended S-meter tweaks, along with the attenuator to hunt down elusive weak signal TRS systems. The telescopic performed well when adjusted to 5/8 wave.
Note that since the bottom element is 8 inches long, you really have no choice - it is too long to adjust for a 1/4 wave anyway.
Not to disrespect the RH-77CA, since I own a few, but I also tested the 5/8 wave measurement on the ungainly RS telescopic. Sure enough, even the RS telescopic adjusted to about 10.5 inches worked better than the 77CA on 800 mhz.
I won't EVEN go into gain figures, antenna patterns etc for the 5/8 wave settings. We're talking about a telescopic antenna with a circuit-board for a ground etc - this is not a fixed-position antenna, but something you can misadjust, so in this application, I'm not even going to try and claim any sort of gain figures at the 5/8 wave positions - just telescope and enjoy.
The Diamond RH789 (bnc) and SRH789 (sma) is a lightweight, good looking telescopic that can be folded at the base if necessary. It is 8 inches collapsed and 31.5 inches fully extended.
For 95-300 mhz, you adjust it to a quarter wave. For 300-1100 mhz, the adjustment is made to being a 5/8 wave. There is a black and silver sticker/chart on the bottom element in centimeters to guide you.
The bottom 8 inch section is black, as well as the bnc / sma connector. The telescoping elements are somewhat dull brushed-aluminum looking. This is a good thing! If the typical RS shiny-chrome "Adam 12" looking telescopic with loading coil puts you off, the Diamond may command a little more respect.
The use of 5/8 wave for above 300 mhz is interesting - there doesn't seem to be any sort of matching device for 5/8 use. Perhaps it isn't really necessary here, since we're not going to encounter much of any sort of swr loss going essentially from the antenna direct to the circuit board. 5/8 wave antennas usually have about 120 ohms resistive impedance with a large capacitive reactance that gets tuned out, but I can see why for a direct-connect whip to a scanner this may not be necessary - although purists will want a matching device.
The intent here is not to turn this into a 5/8 wave antenna thread. Tuning it to a 5/8 above 300 mhz does work.
For example, when the 789 is telescoped out to about 10.25 inches, it works much better than the canonical RH-77CA duck on 800 mhz. The 77 is not "optimized" for 800 mhz, so it is no wonder that a 5/8 wave non-impedance matched whip works better.
For that test, I used a RS Pro-106 with extended S-meter tweaks, along with the attenuator to hunt down elusive weak signal TRS systems. The telescopic performed well when adjusted to 5/8 wave.
Note that since the bottom element is 8 inches long, you really have no choice - it is too long to adjust for a 1/4 wave anyway.
Not to disrespect the RH-77CA, since I own a few, but I also tested the 5/8 wave measurement on the ungainly RS telescopic. Sure enough, even the RS telescopic adjusted to about 10.5 inches worked better than the 77CA on 800 mhz.
I won't EVEN go into gain figures, antenna patterns etc for the 5/8 wave settings. We're talking about a telescopic antenna with a circuit-board for a ground etc - this is not a fixed-position antenna, but something you can misadjust, so in this application, I'm not even going to try and claim any sort of gain figures at the 5/8 wave positions - just telescope and enjoy.