Antenna Experimenting - Glass Mount (Without Glass)

[SharpNEO]

First off, I have no intention of mounting this on a vehicle - my NMO works wonderfully.

I apologize if the bold lettering offends anyone, but I really wanted to emphasize that any experimenting with this thing will be sans vehicle.

The antenna came to me in a box of odd pieces/parts that was given to me awhile ago. And since a big reason I got my ham ticket was to play and experiment, I couldn't resist pondering the potential of this little fella. No sense in letting a good piece of metal go to waste.

(On a side-note, I was eyeballing this tall, ugly lamp in the living room, but my wife suggested I might experience sudden health issues if I touched that lamp... Thus, the glass-mount antenna project was born!)

The antenna is an Opek VUG-270 ( VHF/UHF ) DUAL BAND MOBILE which is a company/brand I have never heard of. I will list the manufacturer (claims) specs at the end of this post.

• My first question is, can this be used without glass (or some other faux capacitor) placed between the contacts? Can I just go ahead and place the two contacts together without causing a safety issue?

I realize that this was designed for just such a purpose, but I'm curious to know what else I can do with it. However, I'm also leery of just plugging things in to my radio and pressing transmit simply to see what happens. Thus, I'm hoping that someone can confidently say that I won't toast anything by using this antenna beyond its intended design.

• Second question, why is the included radial (on the inside connector) at a horizontal angle?

I would have guessed for a radial (counterpoise?) such as this it might work better if it were inline (vertical) with the actual antenna. (Apparently I still have much to learn.)

• Third question, if I can simply connect the contacts and get to safely experimenting, should I rely on the "built-in" tuning apparatus that it claims to have or should I look at getting a manual tuner for SWR?

I haven't really seen anyone using a tuner for 2M rigs in the just few years I've been involved with this hobby, but I haven't exactly asked around, either. I'm sure somebody makes a 2M tuner. But if I can get away with just an SWR meter and tuning the little box-screw, then I'd probably prefer that. (Or perhaps some of you have experience with that little box-screw adjuster and can save me some time by warning me away from it.)

I've edited this post to add a fourth question...

• Question four, is the length of the antenna based upon the coiling in the center?

I would have thought I would need to be around 19 inches or so for a 1/4 wave on 2M, but even having dual-band capability I don't understand the manufactured length of this antenna model.​

In any case, this isn't for primary comms or even an emergency - those are well covered. This is just me wanting to try out my first non-traditional antenna experiment with a somewhat ready-made piece of material. It didn't cost me any extra to acquire it and won't be a huge loss if it turns out to be useless. But it's already here and serving no other purpose, and I'm pretty sure (see REALLY HOPE) I won't need a fire extinguisher if this experiment flops. :lol: So, why not?

Any help, advice, even your experience with similar projects, is welcome and appreciated. Thanks much and 73's!

-

Manufacturer (Claims) Specifications:

• GLASS MOUNT MOBILE ANTENNA 2 METER AND 70 CM
• FREQUENCY: 144-148 MHz / 440-450 MHz
• GAIN: 2. dB Over 1/4 Wave (2 m) and 4 dB Over 1/4 Wave (70 cm)
• V.S.W.R: Less than 1.5:1 Through Bands
• POWER: 50 W (max)
• FIELD TUNABLE
• CABLE: 14′ of RG-58 Cable
• CONNECTION: With PL-259
• 26″ STAINLESS STEEL Whip, With Black Finish.
• LENGTH: 28.35″ ( 720 mm )

VUG-270 ( VHF/UHF ) DUAL BAND MOBILE | Welcome to OPEK

 

[popnokick]

If you don't already have these - get them:
- SWR meter that will work on 2M/70cm
- Field strength meter for same range
... then turn the power down on your transmitter as far as it will go (1 watt or less would be best) and start experimenting with all the questions you asked (i.e. use without glass or other dielectric, different angles on the counterpoise element, adjustment of "built in" tuning, etc.).

 

[SCPD]

Hi Sharp .....Wow, experiments...I love experimenting!
.
Like others have suggested, you aren't going to get into any real truble if you turn your power down to a minimum, and use a good SWR meter- one made specifically for V/UHF- don't skimp here.
That antenna was design to have a glass dielectric between it's tuner box and the antenna element- think of it as a capacitor in series with the antenna rod and coil, which is a long inductor. Its resonance properties are engineer'd around that dielectric's value. Certainly you can try to connect the two plates directly, but I think the results will break your heart...lol... (ie; it won't work well if it works at all.)
The antenna has that counterpoise wire as a simple ground plane. It is, I suppose, supposed to be set at a 45-90 degree angle to the base of the whip... I think if you experiment with it's length and angle you will see some interesting changes in SWR- the optimum should drop it close to 1:1.
That coil in the antenna rod is an inductor that makes this something like (and here I am just throwing in numbers) a half wave on VHF and something like 5/8 or 3/4 wave on UHF.. That tuner boxy-arrangement has a capacitor in it that works in series with the glass dielectric to resonate the whole thing, as it works against that counterpoise.
I don't see any reason you can't switch glass for plastic, and the size of the plate is not important, just so it covers the tuner and the antenna plates. It should be no thicker than a sheet of glass (couple of millimeters) -however.
I think your experimenting is great, and this should provide some interesting hours
.
....................................CF

 

[prcguy]

Since that version has a tuning adjustment I think the spacing between plates with just the adhesive pads is probably fine and you can probably tune it to an ok match.
prcguy

 

[SharpNEO]

Awesome, the replies are much appreciated!

Never considered substituting the window with plastic, or with other glass.

So much to do now!

I'll post some updates after I get some meters, etc., and get things started. (I'm sure there's bigger, better experiments I could be chasing - but, hey, got to start somewhere.)

Thanks much!

 

[wyShack]

Some one actually experimenting-great. Only real comment I would have is that the two boxes are designed to be separated by the rear window of a car-in my mind that would be glass (and a little plastic) that is about 3/8" inch. As other posters have already pointed out, the two boxes and dielectric between them are a capacitor that is part of the antenna's design. My guess is you are going to have to 'match' a rear window's characteristic thickness and dielectric constant fairly close-the trimmer for tuning will cover what the designer thought was the variation in rear windshields.

Being near the unit will have a large effect on tis tuning so you are likely to have to tale a reading, make a small adjustment, then another reading as your body will interact with it.

Have fun