Which Antenna

[radiohuman]

Hi all,

I am looking for a really good antenna for my handheld. I have searched and read many good reviews on the Diamond RH77CA/RH771. However, I found this list of Diamond antennas that the local radio store is selling. I am looking at frequencies around the 100-400mhz, mainly airband. And also a good overall performer. What do you think of these other than the RH77CA/RH771? Thanks.


RH-951 VHF/UHF/1200 MHZ
36 CM, 1/4-L VHF, 1/2-L UHF,
2 X 5/8-L 1200 MHZ,
120/150/300/450/800/900 MHZ RECEIVE


RH-795/799 70-1000 MHZ
TELESCOPIC, 115 CM FULL USE,
10 STAGES
RH-799 FOLD-TYPE AFTER 1 STAGE


RH-771/777 VHF/UHF
1/4-L VHF, 1/2-L UHF, 40CM
RH-777 FOLD-TYPE
120/150/300/450/800/900 MHZ RECEIVE


RH-775/779 VHF/UHF
TELESCOPIC, 41 CM FULL USE,
10 STAGES,
120/150/300/450/800/900 MHZ RECEIVE

 

[N4JNW]

I'm sure any of those would work well. I wouldn't like the fold over one though, or the telescopics. If you're planning on not moving around much with your scanner, then a telescopic would be ok, but if you're like me, I'm in and out of vehicles, in and out of doors all day long. A big long whip might be nice, and will boost your reception, but you've got to look at practicality.

Of course, if you plan on doing some arm-chair only scanning with a glass of lemonade, then a telescopic would probably be a good idea..

 

[radiohuman]

Thanks KG4LJF, I am definately getting the RH771 for outdoor use. I am also thinking of getting the RH795 for my second handheld/indoor use. Its a telesopic that extends to 115cm! What do you think?

 

[N4JNW]

Now remember, the longer you make the antenna, the less resonant it's going to be on higher frequencies, and vice versa.. Meaning, by going too long, you can actually hurt performance, rather than improve it.

I put my 40" telescopic 2 meter antenna on my scanner, and it wouldn't recieve a trunked control channel at all. Because A, it was too long, and B, it wasn't made to recieve in that range, because it was too long.

Telescopic whips have one advantage over duckies. You can change their length, to match what you're trying to recieve. You can optomise your antenna's performance, by knowing what lengths to make it for what you want to hear. Shorter lengths for higher frequencies, longer lengths for lower frequencies.

 

[radiohuman]

Great info, so I guess the telescopic is a better option for indoor use. Could you tell me or point me to a webpage that teaches you on what length to adjust for which frequeuncies? I am also wondering whats the difference between a telescopic that extends to 115cm and one that extends to 40cm. Thats because according to the website, they both seem to receive the same range.

 

[N4JNW]

Yes. If you're indoors, or out, but you're sitting still, the telescopic would be best. If you're walking around, in your car, or in a crowed area, use the duckie. You'll draw less attention to yourself, and not risk breaking the telescopic. Most telescopics are pretty well built, but they can be bent if hit just right.

As far as figuring the length you need to make your telescopic antenna, for a certain frequency range you want to cover, Google 'Antenna length calculator". Using this, you simply type in the frequency you're interested in hearing, and it will tell you how long your antenna needs to be. Measure it, and adjust it, for that frequency and you should get your best performance.

 

[mjthomas59]

Just curious what some of those Diamond antennas are going for at your local shop? I think i picked up my Diamond 77 for about 25 bucks from universal-radio.com Although you do have to wait for shipping, the price seems pretty good and the performance is outstanding. Atleast on everything but 800mhz+.

 

[radiohuman]

Thanks KG4LJF! Could I ask you some final questions. How could you tell the wavelength of the antenna without looking at its specs?

And how does a telescopic that extends to 115cm(1/4 wave) compare to one that extends to 40cm(1/4 wave)? If I use the antenna length calculator to find the length for 130mhz, it gives me 0.549M or 54.9cm. How does that apply to the 40cm telescopic?

Really appreciate all your help.

 

[radiohuman]

Mjthomas, I am not sure how much the other models cost, but the RH711 cost about 12USD. I have not personally checked it out at the store, I have only made an inquiry over the phone. I am going down on Monday to check and buy it.

 

[N4JNW]

No problem. Both antennas you have are 1/4 waves. But one extends longer than the other. This is because there is a coil in the base of the antenna, that makes the antenna "appear longer" to the radio, but to you, it's shorter.

What I mean by appearing longer, is that in order to be efficient, the antenna needs to be a certain length. You know that. But sometimes, that certain length is longer than what people want it to be. People like short, small antennae, but, short small antenna only work well for 400 mhz and up. Because the frequency is so high, they must be short.

It's like a CB antenna. I know you've seen the big 102" whips that off roaders use on their jeeps and trucks. But, I'm sure you've also seen the much shorter CB antennas that truckers have on their mirror, right? They're both CB antennas, but one is much shorter. That's because truckers don't need a big antenna. They only care about talking a couple miles. Off road guys need a big antenna so if they're stuck in the mud, or if they break an axle, they can really reach out and talk to their buddies to get help.

Now, back on track, this also applies to recieving. The closer you can get your antenna to the length it needs to be, the better it will perform. Try locking in on a weak weather radio station, and change the length of your antenna, and see if you can make it come in any better..

 

[radiohuman]

So it is the coil in the base! I guess if I use the 40cm telescopic, there is nothing I could do but just extend it to the max...You have been most helpful..Thanks again and god bless..

 

[radiohuman]

Hi,

I bought the rh771 and rh799 at $12 and $18. I must say that the rh771 worked pretty well, but did out out-perform my current 7100 stock telescopic antenna. The stock antenna does slightly better. However, the 799 is great. I was able to get better reception by adjusting its length(really long antenna). Both are very nicely looking and professionally constructed. I recommend rh795/799 for handheld indoor use.