Tram 1486 issue

[WSBQ643]

I recently purchased two Tram 1486 antenna's. Used the chart that came with it and cut it for 467 to use mainly to connect with repeaters. Tested it and got 2:1 for SWR. Not good. The I cut the next one for 462 using the chart that came with it. SWR's were perfect 1:0. 

The charts attached are not the same and the one I cut for 467 did not have an option for 462 on the tuning sheet but the other one did. Can't quite get my head wrapped around why two different tuning sheet and why the 467 is high on SWR since I transmit on 467. 

Need some help on this from the antenna smart guys out there. 

Thanks

 

[SteveShannon]

14 minutes ago, WSBQ643 said:

I recently purchased two Tram 1486 antenna's. Used the chart that came with it and cut it for 467 to use mainly to connect with repeaters. Tested it and got 2:1 for SWR. Not good. The I cut the next one for 462 using the chart that came with it. SWR's were perfect 1:0. 

The charts attached are not the same and the one I cut for 467 did not have an option for 462 on the tuning sheet but the other one did. Can't quite get my head wrapped around why two different tuning sheet and why the 467 is high on SWR since I transmit on 467. 

Need some help on this from the antenna smart guys out there. 

Thanks

 

On the first one, did you check the SWR before you cut it? Was SWR higher or lower?

It looks like you have two different versions of the antenna.  

[WRYZ926]

26 minutes ago, kidphc said:

Would live to test with that stuff. Alas too poor and will have to test with what you said not to a $100 antenna analyzer.

Sent from my SM-S901U using Tapatalk
 

A NanoVNA will work for showing if you are high or low on your SWR and if you need to shorten or lengthen the antenna. And NanoVNA's can be bought for under $100. There is a bit of a learning curve with them but it isn't that bad.

[GreggInFL]

What vendor(s) would you guys recommend for a pre tuned antenna?

[SteveShannon]

10 minutes ago, GreggInFL said:

What vendor(s) would you guys recommend for a pre tuned antenna?

Midland mxta26.

[GreggInFL]

7 minutes ago, SteveShannon said:

Midland mxta26.

For mobile, base or both?

Thanks, Steve.

[WSBQ643]

Well I can't say I didn't get what I expected to get for an answer. Sometime I just like to try new things. I thought like the comment that these must be two different antennas. I checked their site and they don't have a grms and a HAM. It's supposed to be generic for both. Guess I learned my lesson on this one. Just ordered a pre-tuned 10' comet. We will see how that works out. 

[kidphc]

Now you know why amateur radio guys say trim less than you need. Then tune tiny bits to find a balance with something like a nano vna.

We have tons, usually a stack of antennas whips that were trimmed too much.

Can you get a replacement whip? Sometimes it's less than 1/8" between "oh that works well" and "shit".

Sent from my SM-S901U using Tapatalk

[SteveShannon]

1 hour ago, GreggInFL said:

For mobile, base or both?

Thanks, Steve.

Mobile, but it certainly could be used for base if you give it a mount with a ground plane. The MXTA26 comes without a base. 

[SteveShannon]

51 minutes ago, WSBQ643 said:

Well I can't say I didn't get what I expected to get for an answer. Sometime I just like to try new things. I thought like the comment that these must be two different antennas. I checked their site and they don't have a grms and a HAM. It's supposed to be generic for both. Guess I learned my lesson on this one. Just ordered a pre-tuned 10' comet. We will see how that works out. 

Your investment isn’t a total waste. Although I haven’t tried that antenna I know of forum members who have and got decent results.
Do you have an antenna analyzer so you can sweep it?  

And disregard negative comments from 381. For some reason that’s what he does more often than not.

[Borage257]

If the elements are too short, you may be able to repair it by soldering 12 or 14ga wire on to lengthen the shortened sections

[SteveShannon]

5 minutes ago, Borage257 said:

If the elements are too short, you may be able to repair it by soldering 12 or 14ga wire on to lengthen the shortened sections

I don’t know what the elements are made from. If they’re stainless, soldering becomes more difficult, but StaBrite solder works well for stainless. 
If they’re aluminum you won’t be able to solder them with normal techniques but you could crimp on an extension. I would scour the aluminum surfaces and apply penetrox to the surfaces. 

[WRYZ926]

It is way easier to shorten an antenna versus lengthening one. This is where a cheap NanaVNA or an antenna analyzer comes in handy. You really need to know if the antenna is resonant above or below where you want it.

I had to trim my Tram 1174 antenna. Before I made a single cut, I measured the SWR with an analyzer to see if it was high (short) or low (long). I made small 1/8" or less cuts testing the SWR after each cut. I did this until I was happy with the SWR.

Remember to test at 467 MHz and at 462 MHz. You might get it spot on at 1.0 - 1.2 at one but be around 1.8 on the other. Or you might get both really close. I got my Tram to 1.3 at 462 MHz and 1.5 at 467 MHz. 

You will be fine as long as you are 1.8 or less on both 467 MHz and 462 MHz. Remember to cut just a tiny bit and test after each cut.

If your lowest SWR is above your target frequency, then the antenna is too short. If the lowest SWR is below the target frequency, then the antenna is long and needs trimmed.

[SteveShannon]

8 hours ago, WSBQ643 said:

Tested it and got 2:1 for SWR.

It’s also really important to realize that 2:1 isn’t really terrible. The power still goes out the antenna. In fact you might not even be able to tell the difference between an antenna with 2:1 versus 1.0:1 SWR. 

[nokones]

8 hours ago, SteveShannon said:

Midland mxta26.

Agree, if you want a good VSWR on GMRS freqs.

[nokones]

What VSWR meter were you using?

[nokones]

11 minutes ago, nokones said:

Agree, if you want a good VSWR on GMRS freqs.

Oops, I guess this is a Base Station antenna. I would look into a Laird FG4605 5 dB Omni antenna. No trimming required. If you use quality LMR400 cable and connectors, not that KMR400 crap from Amazon, and keep it around 30 something feet, you'll probably will see low 1 points on the VSWRs, if you only want to do it once and have it last for a long time.

[nokones]

9 hours ago, WSBQ643 said:

I recently purchased two Tram 1486 antenna's. Used the chart that came with it and cut it for 467 to use mainly to connect with repeaters. Tested it and got 2:1 for SWR. Not good. The I cut the next one for 462 using the chart that came with it. SWR's were perfect 1:0. 

The charts attached are not the same and the one I cut for 467 did not have an option for 462 on the tuning sheet but the other one did. Can't quite get my head wrapped around why two different tuning sheet and why the 467 is high on SWR since I transmit on 467. 

Need some help on this from the antenna smart guys out there. 

Thanks

 

Trimming charts are only a Ballpark guess and never cut any antenna short based on the chart. Always use a quality VSWR meter not something that cost around a hundred dollars.

[kidphc]

It is way easier to shorten an antenna versus lengthening one. This is where a cheap NanaVNA or an antenna analyzer comes in handy. You really need to know if the antenna is resonant above or below where you want it.
I had to trim my Tram 1174 antenna. Before I made a single cut, I measured the SWR with an analyzer to see if it was high (short) or low (long). I made small 1/8" or less cuts testing the SWR after each cut. I did this until I was happy with the SWR.
Remember to test at 467 MHz and at 462 MHz. You might get it spot on at 1.0 - 1.2 at one but be around 1.8 on the other. Or you might get both really close. I got my Tram to 1.3 at 462 MHz and 1.5 at 467 MHz. 
You will be fine as long as you are 1.8 or less on both 467 MHz and 462 MHz. Remember to cut just a tiny bit and test after each cut.
If your lowest SWR is above your target frequency, then the antenna is too short. If the lowest SWR is below the target frequency, then the antenna is long and needs trimmed.

I kinda try to get my lowest mid-band. Then take acceptable if the band edges are 1.7 or so.

Sent from my SM-S901U using Tapatalk

[nokones]

16 minutes ago, kidphc said:

I kinda try to get my lowest mid-band. Then take acceptable if the band edges are 1.7 or so.

Sent from my SM-S901U using Tapatalk
 

I always tune for 465 Megs for a decent reading on both 467 and 462 Megs but still take readings on both freqs.

I always tune with a RigExpert 650 Antenna Analyzer and then check the entire antenna system with the radio connected with a calibrated Bird Meter and Elements.

[kidphc]

I always tune for 465 Megs for a decent reading on both 467 and 462 Megs but still take readings on both freqs.
I always tune with a RigExpert 650 Antenna Analyzer and then check the entire antenna system with the radio connected with a calibrated Bird Meter and Elements.

Would love to test with that stuff. Alas too poor and will have to test with what you said not to a $100 antenna analyzer.

Sent from my SM-S901U using Tapatalk

[WRYZ926]

46 minutes ago, kidphc said:

I kinda try to get my lowest mid-band. Then take acceptable if the band edges are 1.7 or so.

Go with what works for you. The main thing is to be 1.8 or less on 462 and 467. An SWR of 2.0 will still work but 1.8 or less is better.

[WRXP381]

For $20 more you could have gotten a 10’ 9db pre tuned antenna and not had to deal with this at all.   Or gotten one of the many 4-5’ pre tuned antennas for the same or less money and had no head ache.  And before some guy that knows nothing about my set up says my antennas don’t last they spend all year up at 30’ with 30-40mph winds every day and 60-80mph winds every week, dry desert air, low teens winters with snow and ice storms and rain and lightening and they still get me more then 200miles with a 20w radio.   Tuning antennas should be saved for the old cb days.