Why do people hate SMA antennas?

Dahwg · Mar 28, 2017

Maybe a silly question, but there is a point I promise.

Ok, so from reading other threads and various reviews, I see that antennas with SMA connectors are much maligned for developing intermittent issues if they are swapped out often. For me this is a problem because as of right now, I've not purchased a mobile rig and so am using a mobile antenna while mobile, and a big Diamond srh70ca when handheld and need to get out, and a little Diamond SRH519 when I need something more discreet or truthfully more wearable in the belt. That is a lot of antenna swapping. Where is the point of breakdown? Is it the antenna or is it the radio? This will only partially go away when I get my mobile rig (soon) because then I could use the cross-band repeat function to extend my range, But may still want the additional reach of a bigger antenna. If the breakdown is in the antenna, then I can live with a $20-$30 replacement from time to time, but if it's the radio, not so much.

Thanks in advance.

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plughie · Mar 29, 2017

Dahwg said:
Maybe a silly question, but there is a point I promise.

Ok, so from reading other threads and various reviews, I see that antennas with SMA connectors are much maligned for developing intermittent issues if they are swapped out often. For me this is a problem because as of right now, I've not purchased a mobile rig and so am using a mobile antenna while mobile, and a big Diamond srh70ca when handheld and need to get out, and a little Diamond SRH519 when I need something more discreet or truthfully more wearable in the belt. That is a lot of antenna swapping. Where is the point of breakdown? Is it the antenna or is it the radio? This will only partially go away when I get my mobile rig (soon) because then I could use the cross-band repeat function to extend my range, But may still want the additional reach of a bigger antenna. If the breakdown is in the antenna, then I can live with a $20-$30 replacement from time to time, but if it's the radio, not so much.

Thanks in advance.

Sent from my LG-H918 using Tapatalk

SMA-F tends to wear out after multiple removals. Many manufacturers put the female end on the radio, making it guaranteed to fail in the long run. If your radio has the pin (Baofeng) you're probably okay. My $600 Kenwood HT has SMA-F and I'm not looking forward to replacing it.

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N4KVE · Mar 29, 2017

Dahwg said:
Maybe a silly question, but there is a point I promise.

Ok, so from reading other threads and various reviews, I see that antennas with SMA connectors are much maligned for developing intermittent issues if they are swapped out often. For me this is a problem because as of right now, I've not purchased a mobile rig and so am using a mobile antenna while mobile, and a big Diamond srh70ca when handheld and need to get out, and a little Diamond SRH519 when I need something more discreet or truthfully more wearable in the belt. That is a lot of antenna swapping. Where is the point of breakdown? Is it the antenna or is it the radio? This will only partially go away when I get my mobile rig (soon) because then I could use the cross-band repeat function to extend my range, But may still want the additional reach of a bigger antenna. If the breakdown is in the antenna, then I can live with a $20-$30 replacement from time to time, but if it's the radio, not so much.

Thanks in advance.

Sent from my LG-H918 using Tapatalk

First I've heard of this.

Dahwg · Mar 29, 2017

plughie said:
SMA-F tends to wear out after multiple removals. Many manufacturers put the female end on the radio, making it guaranteed to fail in the long run. If your radio has the pin (Baofeng) you're probably okay. My $600 Kenwood HT has SMA-F and I'm not looking forward to replacing it.

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Grrr... I have an ICOM IC-t70a and it has the female end on the radio. Though I don't doubt what you're saying is correct, I don't understand why that is the case. It would seem that the part that is prone to failure would be the pin on the male end of the connection. And why would all of these manufacturers run to embrace SMA knowing that these radios are not like public safety radios that are basically set up and then forgotten with some default equipment? Hams are known for tinkering! It seems as though you'd want to make the radio as sturdy as possible and capable of however many modifications would be done. I understand built in obsolescence, but at a certain point, your reputation is going down in flames.

dsalomon · Mar 29, 2017

I'd guess that manufacturers are using them because they are probably less expensive than BNC types. Also, they're much smaller than other mounting types. Space inside most HTs these days is at a premium.

If you're really concerned about it, us a SMA to BNC adapter (and buy BNC terminated antennas), keeping it mounted permanently on the radio. This gives support to the fragile center pin on the female SMA connector.

AK9R · Mar 29, 2017

I think part of the issue is careless operators. The connectors must be very well aligned with no relative angle between then when you start screwing the threads. Misalignment is likely to cause breakage of the center pin or cross-threading.

If I had a handheld that I was using as a mobile which meant I was manipulating the antenna connector regularly, I'd use a good SMA to BNC adapter. The Diamond BNCJ-SMAP is pretty decent and gives some mechanical support if it will fit your radio. There's also a ham named Stephen Gulyas KC2BHO who makes specific SMA to BNC adapters for various radios. They have a rubber collar on them to provide some mechanical support. Google him.

jonwienke · Mar 29, 2017

Any connector will wear out after sufficient remove/install cycles. If you want to extend the life of the radio connector, don't install and remove the antenna every day, or put an adapter on the radio (such as SMA-BNC) and make the adapter take the wear. The radio connector will only experience wear when you change out the adapter, which will extend its life by a thousandfold or so.

prcguy · Mar 29, 2017

I spent the last 30yrs of my career living with SMA connectors professionally, using lots of equipment and cables every day with them. SMA connectors are very robust for their size and can handle hundreds or more connections with no degradation.

Part of my job was using various test equipment that would detect the slightest problem with a connector or cable and I rarely had to swap out equipment or cables due to RF problems.

In my opinion the biggest problem with an SMA connector on something like a scanner is the connector to radio case interface and not the actual connector. I can see people abusing the antenna and stressing out the radio case around the connector because it doesn't have a large surface area to spread out the stress.
prcguy

jonwienke · Mar 29, 2017

prcguy said:
I can see people abusing the antenna and stressing out the radio case around the connector because it doesn't have a large surface area to spread out the stress.

Another reason to use an adapter. A good one will spread out the stress over a larger area than the connector by itself.

Dahwg · Mar 29, 2017

prcguy said:
I spent the last 30yrs of my career living with SMA connectors professionally, using lots of equipment and cables every day with them. SMA connectors are very robust for their size and can handle hundreds or more connections with no degradation.

Part of my job was using various test equipment that would detect the slightest problem with a connector or cable and I rarely had to swap out equipment or cables due to RF problems.

In my opinion the biggest problem with an SMA connector on something like a scanner is the connector to radio case interface and not the actual connector. I can see people abusing the antenna and stressing out the radio case around the connector because it doesn't have a large surface area to spread out the stress.
prcguy

This would seem to indicate that the problem lies more in user error that in design.

This actually makes me wonder if the problem itself is not overstated. So far I've only seen responses that are hypothetical in nature. Of the tens of thousands of devices out there, you'd think there would be more anecdotal evidence of equipment failure. Granted, continually manipulating any metal eventually will eventually wear it down, but that threshold seems like it may not be as eminent as I'd originally feared.

Also, from what I'm reading, it is in fact, the center pin that is the weak point. In which case, the danger to the radio itself is getting a broken pin stuck in the center hole. Maybe not the wort problem to have if you can get it out. Antennas are a lot cheaper than radios.

Does that sound about right?

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prcguy · Mar 29, 2017

I just thought of a potential problem with SMA connectors on radios. The SMA center pin is intended to only slide straight in and out without turning and you should only turn the outer threaded part of the connector to tighten. Most SMA antennas do not have rotating threads separate from the antenna body and you end up spinning the center pin into the female fingers as it goes in. That will accelerate wear and shorten the useful life of the connector.

This would also affect type N, BNC, PL-259 and most RF connectors we use.
prcguy

jonwienke · Mar 29, 2017

Unless you're changing antennas daily, it's not an issue.

R8000 · Mar 29, 2017

The only negative experience I have had with SMA was on my Kenwood F6A. I tipped the radio on it's side once on a table top and the extended length antenna broke the threaded shell right off the chassis mount on the top of the radio. The insulator and center pin were left behind.

I ordered a new chassis mount SMA female from Kenwood parts and it was actually pretty easy to replace.

I think stress on the female chassis mount with a extended length antenna would cause stress cracks over time. I think that is what happened with mine, and the one gentle tip over was enough to sheer it off. An adapter could as well if you use it with stiff/heavy coax that stresses the connector.

jwt873 · Mar 29, 2017

Yea, the SMA connector is fragile.. I found that out the hard way using a BNC adapter on my Kenwood TH-D72. It didn't take much to snap the top of the threads off.

I don't use adapters at all now on my HT's.. I completely gave up using BNC antennas and when I want to connect to something external, I use short jumpers made with thin RG-174 coax.

I put an SMA of the correct polarity on one end and a BNC or PL259 or whatever I want to mate to on the other end. The flexible coax ensures that there is no strain on the SMA connector.

David628 · Mar 29, 2017

For what its worth, concerning my Uniden BCD436 scanner and not my HAM HT: I swap out the portable antennas twice or more daily when going from home to mobile and back. I don't use any external coax cables or extensions. Owned the scanner for a little over a year now and "knock on wood" I have never had any reception issues!

For mobile I use: https://www.scannermaster.com/800_MHz_2_5db_Gain_Professional_Portable_Antenna_p/14-540714.htm

For home I use:
Diamond® Antenna ~ RH951S HT Antenna

N4KVE · Mar 29, 2017

jwt873 said:
I don't use adapters at all now on my HT's.. I completely gave up using BNC antennas and when I want to connect to something external, I use short jumpers made with thin RG-174 coax.

This is the proper solution right here. A 12" jumper will keep any strain off the radio.

AK9R · Mar 29, 2017

Dahwg said:
This would seem to indicate that the problem lies more in user error that in design.

This actually makes me wonder if the problem itself is not overstated.

I believe there's a lot to that. For years and years, amateur radio handheld transceiver antennas used BNC connectors. Then, the manufacturers started switching to SMA. It was different. It appeared to be too small. A few people had problems because of the way they were using them. The snowball started rolling and before you knew it, the amateur radio community "hated" SMA connectors.

N4KVE · Mar 29, 2017

W9BU said:
I believe there's a lot to that. For years and years, amateur radio handheld transceiver antennas used BNC connectors. Then, the manufacturers started switching to SMA. It was different. It appeared to be too small. A few people had problems because of the way they were using them. The snowball started rolling and before you knew it, the amateur radio community "hated" SMA connectors.

They started using the SMA when HT's started getting tiny, as the BNC connector would take up too much real estate on the top of the radio. When you start to screw in the SMA, use very little pressure to make sure you're not cross threading anything. I've never had a problem with any SMA antenna.

N4GIX · Mar 30, 2017

Here's a tip when preparing to screw anything: Carefully turn slowly in the opposite direction until you feel a tiny bump, then gently reverse direction. The bump you felt were the threads lining up.

David628 · Mar 30, 2017

N4GIX said:
Here's a tip when preparing to screw anything: Carefully turn slowly in the opposite direction until you feel a tiny bump, then gently reverse direction. The bump you felt were the threads lining up.

+1

That's exactly how I have been doing this reference my BCD436 post above.

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Why do people hate SMA antennas?

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