Is my grounding OK?

[Handy Andy]

Back in the older days, people used Field Strength Meter function and just stood outside the vehicle with the antenna installed, not permanent, just a simple mag-mount for holding and try out looks, location and how the F/Strength meter responded.

FS meters were popular more then, than today, but it's still possible to get one - they use a little piece of wire, like piano wire - as the antenna and the meter is switched to F/S and the SWR CAL knob sets your needle. Back then Radio Shack had sold SWR meters with Field Strength modes built in for this reason.

You had someone in the vehicle watching you and would key the radio system while you took readings...

You use it (FS antenna) and "SWR CAL" sets the needle to Full scale or a reference mark..

You walked over to the other end or side of the vehicle and do that again

As you take your readings from various "angles" from the antenna as it's mounted - same distance if possible from the antenna - versus hood, or trunk distance is more preferred , you can gain an idea of how much energy is going in one direction or another

This process is one way to determine the actual "radiating" pattern your antenna has.

It can also be used to determine the best location for the antenna to get the most needle deflection - sensed power from it.

RF "ground" is a relative term, but it's a way of interpreting how well the antenna is "coupling" with the vehicles'' (in this case) conductive skin of metal as a radiating element as a means to show how efficiently the system works.

 

[rangelia]

the Field Strength meter sounds like a fine tuning device. I can see how something like that would work now that you explained it. Ill keep my eyes peeled for those at flea markets and stuff. Until then, how much does the grounding system have to do with a SWR meter/readings? From what (I understand), I have good readings. Thanks again

 

[rangelia]

Now that you said something about "FS" function I got to thinking about the SWR meter I have and it has a F.S scale on it that goes from 1 to 10. (but it uses the same needle as the SWR just on a different scale.) Is that the same thing your talking about using??

 

[The DB]

Back in the older days, people used Field Strength Meter function

I use a field strength meter as my primary tuning device even today when I have a VNA (think high end antenna analyzer) at my disposal. It is true that they are not as common today as they used to be, but I highly recommend getting one and learning to use it to tune antennas.

The ground system on an antenna has a lot to do with SWR, and it directly affects it. Their is a reason many people call it the antenna's "other half", it is actually a radiating component of the antenna system.


The DB

 

[rangelia]

Cool thanks! Im gonna go today and reset my SWR (and record readings) and go from there. If I gotta go adjusting my antennas location a little I possibly can.

 

[Handy Andy]

Yes!

It's often mis-(ab)used by lack of interest in both using it and understanding it, yet can help you find the right location and if you already mounted the antenna - can use it to help determine the antennas radiation pattern, and overall strength.

Some use the feature to obtain maximum deflection on the meter by tuning the antenna - to me that's ok, but I would use it with SWR so that once you've got your readings - you can then check and adjust SWR.

When using Field Strength meters, remember radios and or the equipment attached to them, their SWR needs - need to be met. So the Field Strength side can help you find good locations and well as how efficiently the system can work, but you still need to heed the SWR and make sure all parts and parties involved are within their limitations of 50 ohm match (or 75 ohm if you're meter is equipped for it)

 

[Beetle]

When using a typical power/SWR/FS meter, you will need a pair of decent binoculars. Reason being that these meters are very much affected by their surroundings. I've seen some that would give a higher reading if you squeezed the enclosure harder.

Generally, moving your hand around the antenna while trying to take a reading will change the meter indication dramatically.

Best way I found to measure field strength is to find a wooden fence, with posts every ten feet or so. Set the meter on one of the posts. Have your assistant key, and you adjust the meter for full scale. You may notice the reading changing as you move your hand. Can't be helped. Then unkey. BEING VERY CAREFUL NOT TO CHANGE THE METER ADJUSTMENT, carry it to the next fence post, back off ten feet or so and do the key down again. Record everything, move the meter again, and repeat as often as necessary. Or as much as you can stand.

No wood fences? Carry a brick and use it as a meter stand.

And by the way: "FS" probably stands for "Field Strength" in this case. When talking about analog meters, however, "FS" refers to "Full Scale", as in "this meter has a FSD (or FSV) of 50 millivolts DC." That would be "Full Scale Deflection", or "Full Scale Value".

 

[Captain Kilowatt]

When using a typical power/SWR/FS meter, you will need a pair of decent binoculars. Reason being that these meters are very much affected by their surroundings. I've seen some that would give a higher reading if you squeezed the enclosure harder.

Generally, moving your hand around the antenna while trying to take a reading will change the meter indication dramatically.

Best way I found to measure field strength is to find a wooden fence, with posts every ten feet or so. Set the meter on one of the posts. Have your assistant key, and you adjust the meter for full scale. You may notice the reading changing as you move your hand. Can't be helped. Then unkey. BEING VERY CAREFUL NOT TO CHANGE THE METER ADJUSTMENT, carry it to the next fence post, back off ten feet or so and do the key down again. Record everything, move the meter again, and repeat as often as necessary. Or as much as you can stand.

No wood fences? Carry a brick and use it as a meter stand.

And by the way: "FS" probably stands for "Field Strength" in this case. When talking about analog meters, however, "FS" refers to "Full Scale", as in "this meter has a FSD (or FSV) of 50 millivolts DC." That would be "Full Scale Deflection", or "Full Scale Value".

two thumbs up to this. I used to do field strength readings on commercial AM transmitter sites and finding a good location away from large vertical objects like towers or long horizontal power lines was paramount in obtaining a good reliable and stable reading.