stupid 3 part VHF antenna question

[ofer]

i have an older 21 foot 3 part antenna that has been in storage.

I was wondering if the ferrule(metal ends on each piece) is acting as the conductor to join all parts. or do the inside center of both pieces have to touch when pieces are screwed together?

 

[High Wire]

Is there an actual center? If so then yes. Clean up the threads, put it together and do an SWR test.

 

[ofer]

Is there an actual center? If so then yes. Clean up the threads, put it together and do an SWR test.

SWR test what is it and how is it done?

 

[High Wire]

Is there an actual center? If so then yes. Clean up the threads, put it together and do an SWR test.

 

[rgano]

I can google as well as the next guy:

"Standing Wave Ratio (SWR) is non-uniformity mathematical expression. The meter, SWR, is used to measure how good the transmit power signal emitted from a radio is traveling through any antenna system into the atmosphere."

The meter you use needs to be for the frequency range of the antenna you are trying to test.

 

[High Wire]

Can the OP post a photo of the top and middle threaded ends?

 

[ofer]

the center points don't seem to touch. it seem like they will provide continuity to the ferrule itself and therefore all three pieces will be conneted...i think


https://www.trawlerforum.com/forums/attachment.php?attachmentid=118543&stc=1&d=1623780641

https://www.trawlerforum.com/forums/attachment.php?attachmentid=118544&stc=1&d=1623780641

 

[backinblue]

For something as critical as an antenna, I'd be looking at a nice shiny new one. But maybe this is not the primary or only antenna on the boat. Why is an old antenna being pulled out of storage and put into use?

 

[ofer]

For something as critical as an antenna, I'd be looking at a nice shiny new one. But maybe this is not the primary or only antenna on the boat. Why is an old antenna being pulled out of storage and put into use?

I am a little bit of a VHF frick. i venture into very remote places in ca and sea of Cortes as an example. I bought this antenna for my 30 foot planning boat in so cal 20 years back. it seemed a little big for it for daily use.

took is off and stored it. I now have a trawler in Alaska and would like to install it on it.

Just trying to make sure its up to the task before i go through the trouble getting it there.

 

[High Wire]

It definitely has a center conductor and an outer jacket. Two separate conductors. Both have to make solid contact. The outer connection is easy. The center not so much. Measure the ohms of the tip. Then connect the ohmmeter to the coax connector. When everything is screwed together tight the ohms should be about the same plus one or two ohms.

 

[psneeld]

Put it together, plug it into a radio and give it a whirl to see how it performs in the real world. Take it to a marine electronics shop if you can't find someone with a radio to plug it into.

Just because its old doesn't mean it can meet spec, plenty of old antennas put through the ringer installed on boats....this one had the luxury of being in storage.

 

[backinblue]

Put it together, plug it into a radio and give it a whirl to see how it performs in the real world. Take it to a marine electronics shop if you can't find someone with a radio to plug it into.

Just because its old doesn't mean it can meet speck, plenty of old antennas put through the ringer installed on boats....this one had the luxury of being in storage.

I wish someone put me in storage so I feel like I did 30 years ago!

 

[psneeld]

If you were a fiberglass tube and a few bit of metal..........

If it works, then why not use it? Because its older?

 

[Ws1c]

Is it a VHF or HF? Looks like HF, then no inner conductor. How is it connected? Coaxial connector would be VHF. Tab for wire would be HF. HF will require a tuner, VHF direct connection to radio.

 

[ofer]

Is it a VHF or HF? Looks like HF, then no inner conductor. How is it connected? Coaxial connector would be VHF. Tab for wire would be HF. HF will require a tuner, VHF direct connection to radio.

its VHF

 

[ofer]

I have inserted 3 pennies in the joint areas and screwed in. it seems to have a nice good contact.

Is there anything wrong with that other than its stupid

the center points don't seem to touch. it seem like they will provide continuity to the ferrule itself and therefore all three pieces will be conneted...i think


https://www.trawlerforum.com/forums/attachment.php?attachmentid=118543&stc=1&d=1623780641

https://www.trawlerforum.com/forums/attachment.php?attachmentid=118544&stc=1&d=1623780641

 

[diver dave]

I'd try a pencil eraser on that, and then the SWR meter.
I use a small meter made by Workman in the boat. MOD 104. Easily found on line. it also measures power.

 

[ofer]

it looks like the SWR meter measures output from the radio into the antenna. Usually has an in and an out.

could it be connected to the antenna alone. will it measure anything?

I use a small meter made by Workman in the boat. MOD 104. Easily found on line. it also measures power.

 

[backinblue]

it looks like the SWR meter measures output from the radio into the antenna. Usually has an in and an out.

could it be connected to the antenna alone. will it measure anything?

Yes, the SWR meter is connected between the radio and the antenna. Lower number is better. This may help:

https://www.qsl.net/v73ns/swr.html

If it were me, I would connect the antenna to a radio and see if it works doing some basic radio checks. You can play with SWR later if needed, most don't bother if they are getting acceptable performance.

 

[psneeld]

Put it together, plug it into a radio and give it a whirl to see how it performs in the real world. Take it to a marine electronics shop if you can't find someone with a radio to plug it into.

Just because its old doesn't mean it can meet spec, plenty of old antennas put through the ringer installed on boats....this one had the luxury of being in storage.

Post #11...... hmmmmmm

 

[diver dave]

it looks like the SWR meter measures output from the radio into the antenna. Usually has an in and an out.

could it be connected to the antenna alone. will it measure anything?

No, that would a network analyzer, or an antenna analyzer. I have that one too. Much more $.
Antenna analyzer generates its own signal. SWR meters require a separate drive signal. Traditionally, a radio.

 

[ofer]

does an SWR meter also shows watts. A normal VHF radio produces 25 watt with some possible loss due to cabling. will I be able to see that value?

 

[diver dave]

The Workman unit i referenced does measure RF power

 

[ofer]

sorry to keep going i just looked at the SWR chart mentioned.

It seems to me that the higher watt output the better the SWR value will be.

is this correct? in other words a 6watt radio could not produce a better SWR value than a 25 watt output no matter how good the antenna is. correct assumption?

 

[diver dave]

Negative. SWR is a coarse measurement of the health of the antenna. Not related to power levels at all. The confusion may be that poor (high) SWR levels cause unwanted power reflected back by the antenna.

ie. if your car has bad brakes, they are still bad no matter the size of the engine.

 

[backinblue]

SWR is more of a measure of loss between your radio and antenna (and cabling). If everything is perfectly matched, you have a low SWR (approaching 1.0). Mismatches result in a higher SWR and results in power loss.

 

[ofer]

that what a surmised from this Standard VSWR Monograph

https://www.qsl.net/v73ns/swr.html

 

[diver dave]

SWR is more of a measure of loss between your radio and antenna (and cabling). If everything is perfectly matched, you have a low SWR (approaching 1.0). Mismatches result in a higher SWR and results in power loss.

Sort of. But beware. Very long lengths of coax will hide antenna problems due to coax losses. Ie. the longer the coax, the better will be the SWR. So, if its the antenna you want to measure, use a short run of coax.

And feedline loss is not measured with SWR meters. Its rather unrelated. Mismatch is the job of SWR indications. So, you need both mismatch numbers AND loss numbers to show feedline performance.

 

[diver dave]

that what a surmised from this Standard VSWR Monograph



https://www.qsl.net/v73ns/swr.html

That graph shows various absolute reflected power levels vs forward power vs SWR level.
It answers the question “ if i have a 2.5:1 VSWR, and use a 25 Watt radio, how much reflected power is there?

 

[High Wire]

I have inserted 3 pennies in the joint areas and screwed in. it seems to have a nice good contact.

Is there anything wrong with that other than its stupid

Yikes!!! Other than a direct short? Don't bother with a SWR meter. It will just peg bad and the short will destroy your radio.
Get the pennies out of there!