Low Profile VHF Antenna Performance

[lb2910]

OK, good deal. Glad it's working well.

Good evening all... interesting side note to this installation of my VHF-HI antenna... I recently learned the benefits of using an SWR meter to fine tune my antenna to the freq I am using it on. Turns out...(and typical of my luck) I cut the antenna too short when I initially installed it. I'm showing a reading of 3.2-ish. Initial reading was around 3.0 and I cut a very small piece that gave a reading of 3.2. So.. I have to get another STI-CO flex antenna since I am told that reading is awful. I am looking for a reading of 1.2-ish right? In case you're curious, I am using the Surecom SW-33 SWR meter. No, it's not a $1000 version but I read for a hobbyist like me, it does ok.

.....at least I'm learning a lot about this stuff... right??? HAHAHA

 

[west-pac]

Take your antenna off of the antenna mount and see if the SWR changes. If it does not, the problem is in the coax or mount.

 

[krokus]

Good evening all... interesting side note to this installation of my VHF-HI antenna... I recently learned the benefits of using an SWR meter to fine tune my antenna to the freq I am using it on. Turns out...(and typical of my luck) I cut the antenna too short when I initially installed it. I'm showing a reading of 3.2-ish. Initial reading was around 3.0 and I cut a very small piece that gave a reading of 3.2. So.. I have to get another STI-CO flex antenna since I am told that reading is awful. I am looking for a reading of 1.2-ish right? In case you're curious, I am using the Surecom SW-33 SWR meter. No, it's not a $1000 version but I read for a hobbyist like me, it does ok.

.....at least I'm learning a lot about this stuff... right??? HAHAHA

View attachment 107432

Try to find someone that can sweep the cable & antenna for you. A NanoVNA will do the job well enough for hobby use, and local ham probably has one.

 

[lb2910]

Try to find someone that can sweep the cable & antenna for you. A NanoVNA will do the job well enough for hobby use, and local ham probably has one.

Thanks for that bit of advice... I'll admit, I don't know any HAM operators in my area. I did watch some YT videos on using a Nano VNA and.. wow... way too deep in the weeds for me at my level. I am pretty confident that I just cut the antenna too short. When I did the two readings, it coincided correctly with the readings and cuttings. The coax and mount are brand new and I was meticulous with how I did the mounting (thanks to MMcKenna!!). I ordered another Sti-Co Flexiwhip through Antenna Farm and they are fairly reasonable. This time I'll start longer and then cut small lengths until my SWR reads around 1.2-ish.

 

[mrweather]

You can add more antenna length by inserting a spring at the antenna base. But since you've got a new whip coming, make sure to measure twice and cut once this time!

 

[lb2910]

You can add more antenna length by inserting a spring at the antenna base. But since you've got a new whip coming, make sure to measure twice and cut once this time!

Most definitely.. but in my humble defense, I cut the antenna based on the crude chart STI-Co includes with the antenna. I had no idea about the SWR meters to help fine tune the cutting. So as it turns out, I just happened to cut the antenna too short based on all the variables of my mounting, crude ground plane, etc... So THIS time, I'll definitely cut longer and then use the SWR meter to cut until I get to the 1.2:1 reading.

 

[west-pac]

Most definitely.. but in my humble defense, I cut the antenna based on the crude chart STI-Co includes with the antenna. I had no idea about the SWR meters to help fine tune the cutting. So as it turns out, I just happened to cut the antenna too short based on all the variables of my mounting, crude ground plane, etc... So THIS time, I'll definitely cut longer and then use the SWR meter to cut until I get to the 1.2:1 reading.

Have you checked for continuity on your antenna mount? You can do that by using a VOM/DMM. Put one probe on the center pin of the BNC connector, and put the other probe on the outer shell. It should be open, or show no connection. If it shows that they're connected you have a problem with your antenna mount.

Also, I would check the SWR of the new antenna before you start cutting on it; then cut it if you need to.

 

[lb2910]

Have you checked for continuity on your antenna mount? You can do that by using a VOM/DMM. Put one probe on the center pin of the BNC connector, and put the other probe on the outer shell. It should be open, or show no connection. If it shows that they're connected you have a problem with your antenna mount.

Also, I would check the SWR of the new antenna before you start cutting on it; then cut it if you need to.

I'll check continuity tomorrow.... and yes.. I plan on testing the SWR prior to any cutting.. then cut until the meter is showing around 1.2

 

[lb2910]

Have you checked for continuity on your antenna mount? You can do that by using a VOM/DMM. Put one probe on the center pin of the BNC connector, and put the other probe on the outer shell. It should be open, or show no connection. If it shows that they're connected you have a problem with your antenna mount.

Also, I would check the SWR of the new antenna before you start cutting on it; then cut it if you need to.

Confirmed continuity is good...

 

[lb2910]

Question... the Sti-Co Flexi antennas are backordered until late next week... So I won't be able to fine tune/cut a new antenna for a better SWR reading for another week or so... Right now, my reading is 3.2. Is using my XTS-5k with that reading going to harm my radio at all?

 

[mmckenna]

Question... the Sti-Co Flexi antennas are backordered until late next week... So I won't be able to fine tune/cut a new antenna for a better SWR reading for another week or so... Right now, my reading is 3.2. Is using my XTS-5k with that reading going to harm my radio at all?

No, not on a portable radio.
Portable radio antennas suck as is, so it's pretty normal to have high SWR, yet they all survive.
Portable radios also have a poor ground plane/couterpoise, so more antenna suckage going on.

If it's a big concern, keep transmitting to a minimum. Receiving only won't hurt it.

 

[lb2910]

No, not on a portable radio.
Portable radio antennas suck as is, so it's pretty normal to have high SWR, yet they all survive.
Portable radios also have a poor ground plane/couterpoise, so more antenna suckage going on.

If it's a big concern, keep transmitting to a minimum. Receiving only won't hurt it.

Yeah.. I noticed when I put on the Moto factory antenna to get a reading, it was still in the 2.0-2.1 range... So makes sense with what you said..

I will say that even with the 3.2 SWR reading on my current Sti-Co antenna, the range was really decent. I imagine it might only improve slightly with a properly cut antenna and lower SWR, but my main concern was not frying the guts of my beloved XTS-5k radios...

 

[mmckenna]

...but my main concern was not frying the guts of my beloved XTS-5k radios...

I've had many instances where a radio user will damage their antenna, and either tape it back together, or replace it with some random antenna not even designed for the correct band, and the radios still work. I've had end users that took a pair of wire cutters to the antenna because "it was too long and poked me in the ribs", or "I thought the short antenna looked cooler". An SWR of 3:1 for a short period of time won't result in your radio being damaged.

 

[n0xvz]

...so more antenna suckage going on.

I'm not a radio technician, but I'm pretty sure this is a technical explanation.

 

[mmckenna]

I'm not a radio technician, but I'm pretty sure this is a technical explanation.

That it is.

 

[lb2910]

I've had many instances where a radio user will damage their antenna, and either tape it back together, or replace it with some random antenna not even designed for the correct band, and the radios still work. I've had end users that took a pair of wire cutters to the antenna because "it was too long and poked me in the ribs", or "I thought the short antenna looked cooler". An SWR of 3:1 for a short period of time won't result in your radio being damaged.

WOW.... and I thought I was a neophyte when it came to radios. That is insane...

Will the trouble I'm going through to re-cut an antenna for an SWR of around 1.2 from 3.2 be a noticeable performance difference? Or just better for the radio guts over the long term? Either way, I'm still gonna make sure my antenna is cut properly. I was just wondering based on your knowledge and experience.....

 

[mmckenna]

WOW.... and I thought I was a neophyte when it came to radios. That is insane...

Will the trouble I'm going through to re-cut an antenna for an SWR of around 1.2 from 3.2 be a noticeable performance difference? Or just better for the radio guts over the long term? Either way, I'm still gonna make sure my antenna is cut properly. I was just wondering based on your knowledge and experience.....

Unlikely you'll tell a difference on receive, but maybe.
On transmit, it'll help a bit.

It's good practice. I usually set up antennas for 1.3:1 or less if I can.

 

[lb2910]

Ok.. I'm about ready to give up on this whole tuning antenna thing... I got my new uncut (21 inch) StiCo antenna... The main freq I will be using is the itinerant freq of 151.5050. I did an initial SWR reading and got roughly a 1.9 or so... so I started cutting VERY small lengths of the antenna.. the reading kept going up. I figured that since the recommended antenna length is 18.9 inches, the closer I got to that length, the lower the number would get. Well, the readings were all over the place.. I finally got a consistent reading of a 1.4 on the itinerant freq of 158.4075. The freq of 151.5050 was like 2.4... I gave up and stopped cutting and will use the 158.4075 freq since it gave me the best SWR.

That said, is this normal for the "recommended" length to be off by that much? At 21 inches out of the bag, I got the best reading (for 151.5050) when the recommended cut is 18.9 inches. My final length is 19 1/4 inches as it stands now. I also double checked continuity and its good.

I can also assume that the cheaper SWR meter of Surecom SW-33 that I bought might also be the issue? To confirm readings, I put the Motorola rubber antenna on and got a consistent 1.2-1.3. So.... I'm clueless...

Thoughts anyone?

 

[mmckenna]

A couple of things:

-Don't put all your faith in a $44 SWR meter.

-Make sure the SWR meter is properly calibrated using the methods laid out in the directions.

-A less than ideal ground plane is going to impact SWR.

-High SWR isn't going to damage the portable radio.

-Putting the portable antenna directly on the SWR meter isn't going to be accurate.

-If the radio works the way you need it to, don't get hung up on the numbers.

 

[lb2910]

A couple of things:

-Don't put all your faith in a $44 SWR meter.

-Make sure the SWR meter is properly calibrated using the methods laid out in the directions.

-A less than ideal ground plane is going to impact SWR.

-High SWR isn't going to damage the portable radio.

-Putting the portable antenna directly on the SWR meter isn't going to be accurate.

-If the radio works the way you need it to, don't get hung up on the numbers.

Thanks as always mmckenna... yeah.. all your points make sense. I didn't want to spend a ton of money on an SWR that I would use like.. once! So the Surecom seemed to be the logical way to go based on the reviews I read. I was excited about really tuning the antenna to its optimal performance since I did the installation all on my own. I work on my Harley to include most maintenance, repairs, modifications, electrical, etc. I enjoy doing things myself and trying to get it right. One thing I am a firm believer in is.. get the right tool to do the job you're working on. And like you said, I can't put my faith in a $44 meter but I had high expectations... HAHA... I might try to schmooze one of my local radio techs into using their $bazzillon professional SWR meters to tune the antenna for some adult beverages.
...on a side note, I went and got a proper BNC crimper and re-crimped my BNC connection. Its a nice hex shaped crimp that was heat shrinked and capped to keep dust and moisture out when not in use!! Its the small victories!!!

Thanks for all the help to everyone.. especially mmckenna!!! I will hoist a beverage for ya my friend!