800 MHz cell antenna outperforming VHF antenna

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GTR8000

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As a friend of mine is fond of saying, FM stands for "F#%@ing Magic", as this here experience would seem to illustrate:

I currently have one of those Laird/Antenex MBCN mobile>base converters paired with a Laird/Antenex B1323 (3db gain 132-174 MHz 55"). All things considered, it's a pretty good combination, and only cost me $35 for the combo. I'm using it receive-only connected to a scanner to monitor VHF Low, VHF and UHF.

The other day I came across an old Andrew model 229 mobile cell antenna (3db gain 824-896 MHz 13" open coil) I had stored away, and decided to have a little fun with it. The results of my very informal test left me baffled, and a bit miffed to be honest.

First thing I did was open the squelch fully and cycle through the NOAA channels, just to establish a "baseline" with the VHF antenna still mounted. I was able to receive the nearest transmitter 5/5, one distant transmitter 4/4, and another more distant transmitter 3/3.

I then swapped just the antenna itself for the 800 MHz model, leaving everything else untouched. Performed the same NOAA test and was now receiving two transmitters 5/5, one transmitter 4/4, one transmitter 3/3 (that I previously could not receive at all) and a fifth transmitter 2/2.

So, clearly this 800 MHz antenna outperforms a VHF antenna on the 162 MHz NOAA frequencies. Go figure.

For the next hour, I scanned some VHF Low, VHF and UHF channels with the 800 MHz antenna still connected, and noticed an improvement in reception to the frequencies I normally listen to. I then switched back to the VHF antenna to compare and verify what I was hearing.

I expected the 800 MHz antenna to outperform the VHF antenna on the UHF band, which it did. The fact that it outperformed an antenna that is supposedly tuned to the VHF band ON the VHF band definitely surprised me. However I was really blown away that this little 13" antenna was outperforming a 55" whip on VHF Low. This 800 MHz antenna must have one serious sweet spot for the frequencies I listen to most (46 MHz, 154 MHz, 453 MHz) to outperform a much larger VHF across such a wide spectrum. It performed so much better that I've decided to use it instead of the VHF for the time being, just to see what else I can pick up with it that I wasn't hearing previously.

I'm now seriously considering picking up a 5db 800 MHz 24" dual coil model to see if it improves reception further. I wonder if open coil vs. closed coil will impact performance at all.

Any thoughts? Suggestions? Explanations? Similar reactions of "WTF :eek:"? :lol:
 
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GTR8000

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Mounted on a short mast on the roof. Good line of site, a few trees taller than the antenna itself surround the property, and at a good elevation above sea level (1,100').
 

GTR8000

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Yes, there is a ground plane. As I stated, the antenna is sitting on top of a Laird/Antenex MBCN Mobile to Base converter. That device features four 24" radials with a female N connector and a L-bracket to attach it to the mast.
 
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mancow

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It's probably acting as a 1/4 wave with a broad bandwidth, whereas the 5/8 is more narrowly tuned and centered on a range away from the weather band.

I would venture to guess that the RadioShack "sputnik" would outperform them both in your same series of tests.
 

nd5y

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Mancow is right. It will act as shortened center loaded 1/4 wave antenna on high band.
One time I swept a cellular mag mount antenna with one of the network analyzers at work and it was resonant around 172 MHz or so. I wish I could have tried several types and some with a closed coil to see if they were all the same on high band but I didn't have any others.
 

GTR8000

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Ok, I'll buy that regarding the NOAA frequencies...but what then explains the improved reception on VHF Low? Or on the VHF frequencies that the 5/8 is actually TUNED to?!?
 

chrismol1

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800MHz antennas good for VHF reception? its a conspiracy!!! lol
 

KE5MC

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Antenna / Wave propagation theory - 90% science and the other 10% well... lets just say it’s outside the boundaries of science and move on.

That's my story and I am sticking to it.
 

nd5y

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Ok, I'll buy that regarding the NOAA frequencies...but what then explains the improved reception on VHF Low? Or on the VHF frequencies that the 5/8 is actually TUNED to?!?
The longer antenna might be causing your receiver to desense from FM or lower TV stations. Maybe you had a bad connection or are just imagining things.
 

GTR8000

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The longer antenna might be causing your receiver to desense from FM or lower TV stations.
There are no FM or TV transmitters for many miles around. No paging towers either. It's not desense or overload. It's simply a matter of the 800 MHz antenna outperforming the 5/8 VHF, simple as that.

Maybe you had a bad connection or are just imagining things.
:roll: Yeah, that's it...I'm imagining things. Every connection in my system is top-notch, trust me on that. As I've already stated, NOTHING was changed except the antenna itself, every other variable remained constant. That would rule out a "bad connection" as it would affect both antennas, which it did not. I also stated that I first tested with the 5/8 VHF, then the 800 MHz, then went back to the 5/8 VHF. The probability that I was "just imagining things" is 0%. Just for kicks, I swapped out with another VHF antenna I have to rule out a problem with the 5/8 VHF, and again, the 800 MHz antenna outperformed. The probability that I had a "bad connection" which affected ONLY the 5/8 VHF is again 0%.
 

GTR8000

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Antenna / Wave propagation theory - 90% science and the other 10% well... lets just say it’s outside the boundaries of science and move on.

That's my story and I am sticking to it.
Which is exactly my point. In this case there is really no reason to believe the 800 MHz antenna would outperform the 5/8 VHF antenna, particularly on the VHF FREQUENICES THE 5/8 IS SPECIFICALLY TUNED TO!! :eek:
 

SAR923

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You're making an assumption that the 5/8 wave VHF antenna is actually a good antenna. It may simply not be a very good design. I can't imagine any well designed VHF antenna hearing less NOAA stations than a cell phone antenna. I know that my RS 800 rubber duck won't pick up half the NOAA braodcasts on my PRO-97 than my Diamond RH77 will. Exactly what kind of VHF antenna is this?
 

af5rn

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Exactly, SAR. There are bum antennae just like there is bum coax. You never know it unless you switch them out. Chances are that if you exchanged your VHF antenna for a new one of the same model, your results would improve. Not all connection and continuity problems are immediately evident or your fault, so calm down. Nobody was accusing your of doing an incompetent install. The Antenex just might be bad. That doesn't negate your report that the 800 is performing this well throughout the spectrum though, and I'm glad you posted that information.
 

GTR8000

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You're making an assumption that the 5/8 wave VHF antenna is actually a good antenna. It may simply not be a very good design. I can't imagine any well designed VHF antenna hearing less NOAA stations than a cell phone antenna.
Fair point, it may well be a crappy design. I've never had issues with Laird/Antenex equipment, but I suppose there's always a first for everything!

Exactly what kind of VHF antenna is this?
The 5/8? I described it in the first post:

Laird/Antenex B1323 (3db gain 132-174 MHz 55")
 

GTR8000

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Exactly, SAR. There are bum antennae just like there is bum coax. You never know it unless you switch them out. Chances are that if you exchanged your VHF antenna for a new one of the same model, your results would improve.
I noted that I swapped it out for a different VHF antenna (Maxrad 1/4 wave), and the 800 MHz still performed better:

Just for kicks, I swapped out with another VHF antenna I have to rule out a problem with the 5/8 VHF, and again, the 800 MHz antenna outperformed.

Not all connection and continuity problems are immediately evident or your fault, so calm down. Nobody was accusing your of doing an incompetent install. The Antenex just might be bad. That doesn't negate your report that the 800 is performing this well throughout the spectrum though, and I'm glad you posted that information.
Again, a bad connection was ruled out by virtue of everything below the whip itself remaining constant, and the testing being done twice on each antenna (alternating between them). Your exact words were "Maybe you had a bad connection or are just imagining things.". If you want me to "calm down", then don't make a silly statement suggesting that I'm imagining things. I know what my ears heard, I know what frequencies and fixed stations I monitor, and I know when I hear a noticeable improvement in reception!

As far as the Antenex being bad, I assume you mean a less than stellar design. It still picks up well, including distant (50-75 miles away) stations, so I'm going to rule out a physical problem with it. Also please refer back to the fact that I tried this with a third antenna i had, a Maxrad VHF 1/4 wave, and the 800 MHz was still out performing them both. Again, ALL other factors and variables remained constant below the whip itself!


I'm not trying to be argumentative, however I assure you I have checked and rechecked everything else in the system aside from the whips themselves. I am forced to conclude that, for whatever reason, the 800 MHz is simply a better design and/or likes the frequencies I listen to. What possible other logical explanation is there for it performing so well on three distinct bands covering an almost 437 MHz divide?

I'm also painfully aware that using a mobile antenna, even with a ground plane adapter, is a less than ideal way to go. I have plans in the works for a "proper" base antenna, but at the moment I'm restricted to something compact and lightweight. This setup fits the bill perfectly!
 

af5rn

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Okay, for accuracy's sake, I'm not the one who said you might be imagining things, lol. Don't take that one out on me, please.

As for all the connexions being okay, how do you know? Did you run a bench test on the base load to see if it was all intact and not shorted? Antenna loads die. It's a well known fact. It just happens. Sometimes it happens before you even install the antenna. That's why I mentioned switching it out with another identical antenna, not a completely different model antenna. Just like cars, some antennas come from the factory bad. Been there and got the t-shirt. And many of the times that people decide an antenna sucks, it was a problem with that specific antenna, not the entire model line.

What's wrong with yours? I dunno. I've never used it or any like it. I just don't want you walking away with an incorrect assumption before considering all the possibilities. And since you posted this here to begin with, I assumed you wanted to discuss it.
 
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