Trying to find out how to properly measure antenna SWR and Watt readings

[LostSignal]

Hi all,
Well, to any of the mods and what not, it's been quite some time since I've last logged ON and after reading the "Warning", I REALLY HOPE I am not doing this thread incorrectly or anything as that is not my intentions at ALL!!!

So, to the point as much as I can... I have multiple SWR/Watt meters (i.e. a Diamond SX-200, SX-400, a cheaper Philmore, etc). I know the cables I have are "good" as I get same/similar readings/results. I will continuity check them, but again, I doubt the countless cables I have, PL-259 to PL-259 "store bought" premade type cables are bad.

So, what happens is, I'm trying to simply connect my Boafeng UV-5RA, for example, and the original antenna it came with along with other dual band antennas with one of them being a Diamond SRH701 dual band, making sure to connect the transmitter end to the input side of the SWR meter and the antenna to the output side. Pretty straight forward as it is labeled on the back of the meter. This is done with my PL-259 connectors and just a few adapters to make the connections. I'm using a "pigtail", if you will for my transmitter side so as to not put strain on the sma connector. That pigtail is also "store bought", from HRO... so I highly doubt there is anything wrong with that connector as well.

What I seem to find is that, after calibrating for SWR measurement reading, for VHF, I transmit on L or H and sometimes my SWR will be within around a 2 or below or sometimes +5 to 1 or some ugly SWR reading? Then, as I moved my Boafeng HT closer to the meter, it seemed to DROP in SWR???

My question is this, does cable length and being a certain distance away have to be done in order to get the correct SWR reading? How do I know what the correct reading really is? I really don't know how else to ask the question on this and hope someone can somewhat understand what I am trying to say here?

Finally, I'm doing an "experiment" with 2m and 70cm with antennas and cable lengths, if you will, and this happen to come up along with questioning what is right and wrong when taking SWR measurement readings.

And actually, my actual final question for now is, does the cable actually become part of the antenna system? Meaning, once I get SWR readings with a certain cable length, does that cable length HAVE TO BE part of the end result with the final build of the antenna cable system? If I get an acceptable SWR reading, say with a 2ft cable as strictly as an example, do I have to leave it at 2ft cable length or can I change the cable length to shorter or longer just as long as it is a 50ohm cable???

Boy, I REALLY hope I am making sense with what was just stated above for someone to help me with this and hope it ultimately helps someone with a similar issue and/or question?

-LostSignal

 

[nd5y]

So you are trying to test hand held antennas with:
hand held radio > coax jumper > meter > antenna
If that is correct then you will never get meaningful readings that way.

 

[LostSignal]

So you are trying to test hand held antennas with:
hand held radio > coax jumper > meter > antenna
If that is correct then you will never get meaningful readings that way.

Yeah, simply put... very well put!!!

What would be the difference when connecting to, say a mobile unit? The meter doesn't know what the source is and/or what the "receive" end is?

If this is the case, then WHAT a noob I really am???

I'm simply doing an experiment, ultimately using a VHF or UHF transmitter unit to a, hopefully, in the end, homemade or "store bought" antenna. Whatever the case, but the SWR is my main focus first on how to properly use one and tune the system, but apparently, that is NOT the case here?

EDIT: does it have to do with "ground plane"???

 

[cmdrwill]

EDIT: does it have to do with "ground plane"???

Exactly, the 'ground plane' IS the other half of an antenna system. And most all hand held radios do not have enough ground plane.

 

[LostSignal]

Exactly, the 'ground plane' IS the other half of an antenna system. And most all hand held radios do not have enough ground plane.

Other than just saying "Goo gle", can you steer me in the right direction on building an antenna and antenna system ultimately using a "transmitter like" VHF transmitter. An example would be something like those compact transmitter "modules". Eventually, I would like to build my own, simple mind you, but build my own VHF and/or UHF transmitter module along with the antenna. But, at the same time, be able to tune the system as well.

With that said, would that require a service monitor? For example a General Dynamics R2670 Service Monitor, which are pretty expensive... in order to accomplish what I want to do?

OR another question would be... how to incorporate the required "ground plane" or is THAT even possible since you say that most all HT's don't have enough ground plane?

In either case, I apparently have some serious reading to do and don't mind doing so, but if at all possible, help steer me in the right direction to start out with.

Thank you guys so far for at least answering my questions. At least now, I know why my readings just did NOT make any sense? They'd be fine one moment and the next, HIGH SWR, but yet the output power, if I was to set it to LOW, the meter seemed to read the correct output power. If I set it to HIGH, then the meter would show right around 4-5W, which is about right. But the SWR just seemed to be ALL OVER the place??? At least now I know why.

So, my last question at least for now, can I incorporate a ground plane to compensate???

Sorry for bothering you guys, I'm trying to get into understanding and building antennas and maybe even make a transmitter for experimenting with...

EDIT: just this little bit and I've actually learned quite a bit.

 

[prcguy]

Sounds like you are trying to measure the rubber antenna that came with the hand held. That is very tricky because with a 1/4 wave whip like that, the SWR meter, the cable to the radio, the radio and your hand are part of the "antenna system" and if you move or change anything the SWR will change. There are special hand held radio dummy boxes with antenna connectors and RF chokes and cable decoupling that companies use to simulate the antenna on a hand held for testing and that takes out some of the external influences that you are finding.

I would try your meters on a base or mobile antenna with proper ground plane so you can see what the meters will do under good test conditions. Then you could try your original setup again with two or three snap on ferrite beads (#43 mix) on the coax right at your SWR meter and keep your body and hands away from the meter and rubber antenna when doing the measurement. You might be able to stabilize your setup and a longer cable would help you get away from the antenna. I would also prop the meter with rubber antenna up off the ground away from any metal using something non conductive like a wood ladder.

 

[LostSignal]

Sounds like you are trying to measure the rubber antenna that came with the hand held. That is very tricky because with a 1/4 wave whip like that, the SWR meter, the cable to the radio, the radio and your hand are part of the "antenna system" and if you move or change anything the SWR will change. There are special hand held radio dummy boxes with antenna connectors and RF chokes and cable decoupling that companies use to simulate the antenna on a hand held for testing and that takes out some of the external influences that you are finding.

I would try your meters on a base or mobile antenna with proper ground plane so you can see what the meters will do under good test conditions. Then you could try your original setup again with two or three snap on ferrite beads (#43 mix) on the coax right at your SWR meter and keep your body and hands away from the meter and rubber antenna when doing the measurement. You might be able to stabilize your setup and a longer cable would help you get away from the antenna. I would also prop the meter with rubber antenna up off the ground away from any metal using something non conductive like a wood ladder.

Everything you and the others have stated are correct!!!

Yeah, I didn't know there were special "hand held radio dummy boxes" along with other accessories to simulate the antenna on a hand held? Wow... NOW I know THAT much more!!!

Well, like I said, I don't mind doing any reading or more research on my own. I apparently need a starting point and I think, with what you and the others have stated, I HAVE a good enough starting point to work with.

Btw, thank you for the "then you could try..." input as that sounds as if that will help me quite a bit.

I do have a CB mobile that I'm pretty sure I could, at least, use for testing with as well as a CB mag mount. I need to find a piece of sheet metal, I imagine, to give it SOME SORT OF ground plane?

But yeah, it may be a few weeks to a few months, but maybe I'll try to show a picture of the end result. All I know right now is that I've got some reading to do and some initial testing of what I have to better understand, as you have said, how to properly do this.

Anyways, THANK YOU ALL for the input thus far!!! I will try to show some pictures of my test setup and what not when I finally get that going.

-LostSignal

 

[W5lz]

Would you have to use the same cabling, meter, ect, to keep the same reading of SWR? Yes. Change any of those and the SWR will change also. What really makes it 'fun' is that you, when you are holding that HT are part of the 'ground' also. Move your hand closer/farther away when doing that measuring... nasty, huh? The thing is that yes, you can make a stable 'fixed' antenna system if you want to. But that means not using that rubber-duck to start with. (Can you see the cost rising already?) Use an antenna of some sort that has it's own 'grounding' or groundplane, it's "other half". HT positioning and whatever it's near will still come into play, but it's sort of minimized, becomes 'standard' and then compensate by tuning that antenna.
Does all of this sound like "worm stew" yet? Yeah, it is, but there is never just one way of doing it. Easiest way is don't worry all that much about it. Really!

 

[LostSignal]

@nd5y @cmdrwill @prcguy

I found a really good write-up that I'm reading right now and will be looking for more articles like this so I can understand more. Also, it sounds like dealing with a vertical first will help me understand the very basics of antennas.

Good lord people, I canNOT thank you enough for at least letting me know and explaining to me!!! Again, THANK YOU thus far with your guys help/input!!!

Antenna Ground Plane: Theory & Design » Electronics Notes

Using an antenna ground plane can enable a simulated ground to be made and allow the antenna to be mounted above ground

www.electronics-notes.com

 

[LostSignal]

Would you have to use the same cabling, meter, ect, to keep the same reading of SWR? Yes. Change any of those and the SWR will change also. What really makes it 'fun' is that you, when you are holding that HT are part of the 'ground' also. Move your hand closer/farther away when doing that measuring... nasty, huh? The thing is that yes, you can make a stable 'fixed' antenna system if you want to. But that means not using that rubber-duck to start with. (Can you see the cost rising already?) Use an antenna of some sort that has it's own 'grounding' or groundplane, it's "other half". HT positioning and whatever it's near will still come into play, but it's sort of minimized, becomes 'standard' and then compensate by tuning that antenna.
Does all of this sound like "worm stew" yet? Yeah, it is, but there is never just one way of doing it. Easiest way is don't worry all that much about it. Really!

HAHAHAHA, yeah, I noticed many, MANY of the things you're describing!!! For example, I noticed moving my hand closer/farther away... and YES, "nasty"... and that doesn't even describe THAT enough!!! HAHAHAHAHAHA *facepalm*

Btw, yeah, it would have to be the "same system" in the end. So, you are correct on that as well.

This is actually going to be pretty fun to do and likely headbanging as well from time to time. But, learning for sure!!!

 

[LostSignal]

UPDATE:
I did an EXTREMELY CRUDE setup of installing "ground radials" and will be updating as I go along, if you guys want to see it??? Still learning and reading, but also excited as it is hard to wait to try to "build something from scratch"!!! Right now, I'm just dealing with the very basics and studying/reading. I was able to "stabilize" the SWR on both H/L settings. I even run my hand around/near and it never goes above a 3... it CLIMBS, but goes back down to a reasonable SWR reading and this is on 2m and/or 70cm. Again, I'm still learning and reading and applying what I'm reading to help me understand as I go along.

Thank you SO MUCH guys for your kind input on this. I'm SUCH a NOOB!!! At least I was on the correct path in thinking it was a ground plane issue and I AM learning.

Anyways, again, THANK YOU guys!!! I'll keep this post updated and hopefully, eventually with some pictures?

-LostSignal

 

[LostSignal]

Another quick question I do have though and BELIEVE ME, I TRIED GOOGLIN G using various wording and such...

My question is:
How do they make a 2m antenna only about, say around 6in tall or there abouts??? What is going on underneath that manufactured molding and such???


Is there simply wire wrapping going on underneath at the base of that antenna, for example? This is one of the antennas that I have as well.

 

[W5lz]

That bottom thicker part houses a loading coil which electrically makes the antenna 'seem' longer. Basically adding inductance via that coil.

 

[LostSignal]

That bottom thicker part houses a loading coil which electrically makes the antenna 'seem' longer. Basically adding inductance via that coil.

So, just like I see on my CB antenna, the wire wraps from the bottom and gets tighter and tighter on the windings at the very top.

Thank you!!!

 

[nd5y]

Probably similar to this:

http://www.rudolf.net.pl/sp9kat/wp-content/uploads/stuff/trx/baofeng/uv5r/schematic/nagoya%20701%20antenna.pdf

 

[rja1]

Do a Bing search for "VHF Tiger Tail". These were popular in the 1990's. Just an 18" piece of wire soldered to a ring terminal that slipped over the BNC connector on your HT. It was just a 1/4 wave counterpoise. Without one of these, YOU are the rubber duck antennas counterpoise.

Bob
N2OAM

 

[KE5MC]

So, just like I see on my CB antenna, the wire wraps from the bottom and gets tighter and tighter on the windings at the very top.

Thank you!!!

The turns per inch may or may not change depending on manufacturer design objective. Also a capacitor may be part of the design too. They can hide a lot inside the base of the antenna.

 

[jim202]

Trying to play with a portable antenna for getting it on the frequency you want can be trying. The best and simple way is to get the info on the antenna you have and look for the cutting chart the company that supplied it.

Normally there is a helical coiled length above the base that looks like a very small door spring to close a door that is incased in the rubber type coating. The cutting chart will indicate how long the long top section of the whip should be for the frequency range your trying to use.

You could consider a mobile radio and a mag mount to put on the roof. It isn't that hard to install one. If your into learning about radios, you might consider an old radio like a Motorola Spectra. They come in different bands line low band, VHF and UHF. It is not that hard to put them on the ham frequencies. Plus there is plenty of info on the Internet about them. The down side is you need a computer with a clock speed around 1GHz or lower to be able to run DOS operating system on it. Then it will take a RIB (Radio Interface Box) to go from the serial port on the computer to the RIB.

You can make your own cables to go from the computer and the RIB. Then make your own cable to go from the RIB to the radio. This same cable will fit all the Spectra mobiles except the front dash mount radio. This takes a different cable from the RIB to the radio.

The web site called Batlabs contains all the cabling information you will need.

If your more comfortable with a commercial radio, then go out and buy one. There are a good number of them on the market that are sold by many companies.

You can use a mobile in your home, but it will take an AC power supply to provide the need current to match what the transmitter requires with a little to spare. A simple dipole antenna will get you started.

There are some very knowledgeable people on the board here. So if you have Questions, just ask away and someone will come back and provide some help.

You might get on the Internet and do a search to see if there is a ham club near you. Go to some of the meetings and get to know the people there. You might even find someone to take you under their wing and be a mentor for you.

Jim

 

[W5lz]

So, just like I see on my CB antenna, the wire wraps from the bottom and gets tighter and tighter on the windings at the very top.

Thank you!!!

It may spiral up the antenna (helically wound) or there could just be that coil at the bottom and a single conductor to the top (most common). It amounts to about the same either way.

 

[MUTNAV]

As a side note, you may want to look at the use of the -239 connectors on UHF, they really don't do very well in that frequency range.

Also,
If you want to measure JUST the antenna, try and take as many of the cables out of the picture. Since any cable losses will make it look like the SWR is lower than the antennas mismatch. Something to remember is that the SWR reading is power going in direction towards the radio, usually it's from the signal being reflected by the antenna, but if you are near another transmitter, you'll be reading the other transmitted signal.


Also.
Your excitement about the subject is very encouraging. Thank you.

Joel