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UHF frequency antennna ( 462 mhz ) tuned to what VHF frequency


Elkhunter521
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For my 771G...

My MFJ-266C (through too many adapters: N->UHF->SMA) shows an SWR of 2.2:1 @ 166MHz. (And it is reporting "Output Error" on the UHF setting, time to dig out the other analyzer).

MFJ-269C shows SWR of 2.7:1 @ 467.1MHz -- not all that good for repeater inputs. And 2.6:1 @ 462.xMHz. It's actually BETTER at 160MHz (That's just above MURS frequency), with this analyzer showing 2.1:1 SWR.

 

In contrast, a 701C dual-band is showing (MJF-269C):  >5:1 SWR, unusable at UHF, and shows 1.5:1 @ 158MHz (I've seen 1.3, depending on just how I hold the analyzer), 2.2:1 @ 154MHz (MURS). The sleeve implies it is tuned for 155&455MHz with SWR <1.5:1 -- Well, the 158Mhz reading passes. The MJF-266C reports 5.4:1 @ 467MHz, 5.2:1 @ 462MHz (best UHF 4.2:1 @ 372MHz). 2.1:1 @ 154MHz (best VHF: 1.7:1 @ 157MHz)

The stock VHF antenna (MURS-V1) runs 1.4:1 at 146MHz -- perfect for the 2m Amateur band; 2.5+ at 154MHz (which is why the MURS-V1 is wearing the 701C).

Stock VHF/UHF (GMRS-V2) shows 1.1:1 at 147MHz -- another match for 2m Amateur. 3.0:1 at 154 (MURS). 2.9:1 @ 431MHz; 3.3:1 @ 467 (GMRS repeater inputs) and 3.6:1 @ 462 (GMRS simplex) (which is why the GMRS-V2 has the 771G -- <3.0 is better than >3.3)

 

Put your money down, and roll the dice!

 

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Ahh, but you can't measure SWR of HT antenna. The radiating element is not 771G, it is 771G + body of the HT. The results acquired by breaking real antenna in two parts and sticking SWR meter in between mean nothing, really.

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2 hours ago, axorlov said:

Ahh, but you can't measure SWR of HT antenna. The radiating element is not 771G, it is 771G + body of the HT. The results acquired by breaking real antenna in two parts and sticking SWR meter in between mean nothing, really.

One, HT antennas are normally quarter wave. There is nothing that prevents a quarter wave antenna from being mounted through other transmission lines. The antenna connectors have two parts, the central pin, and the shell. the shell is conductive and is what couples to the HT body. If using an SWR meter, the shell is connected through the meter to the signal source. Other than insertion losses there is no real difference in the "ground plane". Otherwise one couldn't use things like a car window mount with cable to put the HT antenna outside the vehicle.

Two, I was using an antenna analyzer, not a "through" power/SWR meter. The antenna was directly connected to the analyzer port (not even a cable between them); the analyzer is the signal source, and the body becomes the "ground plane" which further couples to my hand holding the analyzer.

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32 minutes ago, KAF6045 said:

One, HT antennas are normally quarter wave. There is nothing that prevents a quarter wave antenna from being mounted through other transmission lines. The antenna connectors have two parts, the central pin, and the shell. the shell is conductive and is what couples to the HT body. If using an SWR meter, the shell is connected through the meter to the signal source. Other than insertion losses there is no real difference in the "ground plane". Otherwise one couldn't use things like a car window mount with cable to put the HT antenna outside the vehicle.

HT antenna is not a quarter wave with ground plane. There is no ground plane. HT antenna is off center fed dipole. Inserting SWR meter into one leg of the dipole changes antenna. You would be measuring different antenna, not the one that HT resents by itself + the thing everybody calls "antenna". Also consider that if there is any matching components in the HT, they are now behind your measuring device and not taken into account.

32 minutes ago, KAF6045 said:

Two, I was using an antenna analyzer, not a "through" power/SWR meter. The antenna was directly connected to the analyzer port (not even a cable between them); the analyzer is the signal source, and the body becomes the "ground plane" which further couples to my hand holding the analyzer.

Maybe this is somewhat "closer" to when you attach the "antenna" to HT directly. And there is still no ground plane to be found, only the other leg of the dipole. But how close nobody knows, and there is no way to tell. And matching schematics is left in the HT.

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14 minutes ago, marcspaz said:

I can't believe we're talking about testing HT antenna SWR again

We talk about Motorolas, mag mounts, Line A, channelnineteen, Baofengs all the time. Nothing wrong with a good discussion. This is how we get good info and new ideas. Only a certain youtube darling was born knowing everything, just like Saint Alia of the Knife. Normal people learn from conversations and exchange of ideas, me and you included.

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5 hours ago, axorlov said:

HT antenna is not a quarter wave with ground plane. There is no ground plane. HT antenna is off center fed dipole. Inserting SWR meter into one leg of the dipole changes antenna. You would be measuring different antenna, not the one that HT resents by itself + the thing everybody calls "antenna". Also consider that if there is any matching components in the HT, they are now behind your measuring device and not taken into account.

Then all the Amateur radio studies that suggest wrapping a length of wire around the base of the antenna to act as a counterpoise must be nonsense (for 2m, I believe a 19" wire dangling from the connector shell is the recommendation -- 19" is about half of a dipole; the common Rubber Duck coils the equivalent length to create a shorter antenna [of course, said coiling requires some modelling as it begins to act as an inductor, one has to cancel out the inductance, possibly with a capacitive section]). Counterpoise wires aren't used with dipoles, but are used with quarter wave antennas.

https://ham.stackexchange.com/questions/644/handheld-dipoles

https://ham.stackexchange.com/questions/495/how-do-handheld-antennas-work-without-ground

 

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1 hour ago, KAF6045 said:

suggest wrapping a length of wire around the base of the antenna to act as a counterpoise must be nonsense

It's not a nonsense. It is a modification of the existing dipole in an attempt to improve it. By attaching counterpoise you change the currents in the whole antenna, changing many things: pattern, efficiency, SWR, etc. The rationalization of the length (19") comes from the desire to have a center fed dipole (on 2m). Sometimes it helps, often it does not.

Here a link with the proper HT antenna testing method explained, and also experiments with counterpoise that show that they are not always good thing to have: https://www.hamradio.me/antennas/ht-antenna-comparisons.html

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@axorlov. That link makes me want to toss my SRH77CA in the trash.  I am going to try to replicate that test with an FT-65 and an FT3DR to see what my results are like. I'll start another thread after it's done. I need a few days.

 

Great link. Thanks for sharing. 

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agreed...makes me wonder how good that SRH701a that came with my vx7r is doing (though i usually swap have a srh320a triband on instead, or occasionally the 940 to see what little there is to hear on 6m). or diamond in general...  (moving the mostly off topic musings to another thread...)

 

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