SDS100: SDS100 Modified to Accept all SMA Portable Antennas Without SMA to BNC Adapter

trentbob

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Very interesting. Did you make this part yourself? It looks like you just screw it in.

If you mass produce them, I'll take one! :)
 

jonwienke

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He milled off the collar around the SMA connector. IMO it's a bad idea for several reasons:
  1. There is no standard for how far a SMA connector is supposed to protrude from the retaining nut or the radio case. So no matter how much of the collar you shave off, you're going to have fitment issues with some SMA antennas. Some will expect the connector to protrude more, and some less.
  2. BNC is standardized in that regard, so any correctly manufactured BNC antenna will fit on a BNC connector.
  3. BNC connectors are designed to handle more connect/disconnect cycles before wearing out than SMA connectors.
  4. BNC connectors are stronger than SMA connectors, and less likely to break if you drop the radio.
  5. Using an adapter shifts the wear of changing antennas to the adapter. If the adapter wears out, changing it is equivalent to one SMA antenna swap. That decreases wear on the SMA connector by a factor of 1000 or more.
  6. A properly designed SDS100 BNC adapter uses the collar for support, transferring much of the impact stress if you drop the radio to the case instead of the SMA connector. That is the biggest problem with the factory adapter.
 

kd2pm

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As cheap as the adapters are which you can usually find at hamfests...just nice to have a few of those around and use whatever SMA or BNC antenna you have lying around without having to buy 2 versions of the same antenna...I have adapters for both SMA and reverse SMA (DMR radios use those).
 

got2listen

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Very interesting. Did you make this part yourself? It looks like you just screw it in.

If you mass produce them, I'll take one! :)
No extra parts, just enlarged the clearance so a standard-sized SMA antenna would fit. I live within two miles of the 100-watt tower, and don't really need an antenna at all, anything with gain overloads the poor thing. I just like the slim battery and low-profile antenna convenience. It doesn't get knocked anymore.
 

got2listen

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He milled off the collar around the SMA connector. IMO it's a bad idea for several reasons:
  1. There is no standard for how far a SMA connector is supposed to protrude from the retaining nut or the radio case. So no matter how much of the collar you shave off, you're going to have fitment issues with some SMA antennas. Some will expect the connector to protrude more, and some less.
  2. BNC is standardized in that regard, so any correctly manufactured BNC antenna will fit on a BNC connector.
  3. BNC connectors are designed to handle more connect/disconnect cycles before wearing out than SMA connectors.
  4. BNC connectors are stronger than SMA connectors, and less likely to break if you drop the radio.
  5. Using an adapter shifts the wear of changing antennas to the adapter. If the adapter wears out, changing it is equivalent to one SMA antenna swap. That decreases wear on the SMA connector by a factor of 1000 or more.
  6. A properly designed SDS100 BNC adapter uses the collar for support, transferring much of the impact stress if you drop the radio to the case instead of the SMA connector. That is the biggest problem with the factory adapter.
I have both Remtronix REM-810S and REM-800B, and lots of other BNC antennas for lower bands, but this low profile, and slim set-up seem to work well for my environment. I did not mill-off the SMA collar, I just enlarged the opening to accommodate a standard SMA antenna diameter. I don't plan to drop or submerge this portable receiver. This was not intended to be an industrial-strength solution; it was just for my convenience and aesthetics. And by the way, I have old hand-held wide-band receivers that have worn out BNCs. The bottom of the nubs is halfway gone. I wonder if there is more surface area contact of the fine threads of the male SMA vs. bottom of the BNC nubs, just curious. I don't swap antennas much on this receiver, so it is not much of a concern for me, but that's not to say it is the best solution for others.

I do like your low-profile SMA to BNC adapter and will purchase one.
 

jonwienke

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And by the way, I have old hand-held wide-band receivers that have worn out BNCs. The bottom of the nubs is halfway gone. I wonder if there is more surface area contact of the fine threads of the male SMA vs. bottom of the BNC nubs, just curious. I don't swap antennas much on this receiver, so it is not much of a concern for me, but that's not to say it is the best solution for others.

I do like your low-profile SMA to BNC adapter and will purchase one.
Any connector will wear out eventually. BNC takes longer because its a straight push/pull to (dis)connect rather than turning multiple rotations. The nubs on the outside of the BNC female aren't for electrical contact; they are for mechanical locking only. The electrical contact is made with the petals on the male connector engaging the inner surface of the outer tube of the female.

If you order one of my adapters, make a note that you modified your radio. They're machined to fit the stock hole diameter for structural support, so impact stress is transferred to the case shell as much as possible. They won't fit right if the hole is larger than expected.
 

trentbob

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No extra parts, just enlarged the clearance so a standard-sized SMA antenna would fit. I live within two miles of the 100-watt tower, and don't really need an antenna at all, anything with gain overloads the poor thing. I just like the slim battery and low-profile antenna convenience. It doesn't get knocked anymore.
It sounds like you would be a good candidate for the comet CH - 32 miracle baby. It has a recessed BNC and I don't think it's longer than 3 in. It's supposed to be a tri-band but frankly it only works on 7 - 800 megahertz and UHF 2. Very low profile and would look cool on your radio. Look it up if you don't already know it.
 

got2listen

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It sounds like you would be a good candidate for the comet CH - 32 miracle baby. It has a recessed BNC and I don't think it's longer than 3 in. It's supposed to be a tri-band but frankly it only works on 7 - 800 megahertz and UHF 2. Very low profile and would look cool on your radio. Look it up if you don't already know it.
I actually have an old one without the text on the side, this replaced it. It worked great for me on upper 800 MHz but not as well as the Diamond SRFH10 on VHF. I also didn’t like the way the Uniden-supplied SMA to BNC looked with it, but I see Jon’s looks nicer.
 

iMONITOR

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It sounds like you would be a good candidate for the comet CH - 32 miracle baby. It has a recessed BNC and I don't think it's longer than 3 in. It's supposed to be a tri-band but frankly it only works on 7 - 800 megahertz and UHF 2. Very low profile and would look cool on your radio. Look it up if you don't already know it.
Yes I agree. The Comet CH-32 is one of my all time favorites. Some swear at it, but I swear by it. All the technical guys with thousand invested in high end analyzers will chime in on how it can't work well but I've been using it for decades on numerous radios and for me and my needs it works great!
 

tumegpc

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He milled off the collar around the SMA connector. IMO it's a bad idea for several reasons:
This is coming from a guy that drills a hole out of the back of scanners and removes the belt clip to add GPS. LOL
I mean this in a funny way!

I think it's a nice mod to a poorly designed SMA connector. There many HT radios that have SMA connectors and never require any special adapters and been around for many years.
 

jonwienke

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This is coming from a guy that drills a hole out of the back of scanners and removes the belt clip to add GPS. LOL
I mean this in a funny way!

I think it's a nice mod to a poorly designed SMA connector. There many HT radios that have SMA connectors and never require any special adapters and been around for many years.
It's actually fairly common to need washers or spacers between the antenna and radio to get SMA antennas to fit right. As to the rest of your comments, :rolleyes: ...
 

jonwienke

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Yes I agree. The Comet CH-32 is one of my all time favorites. Some swear at it, but I swear by it. All the technical guys with thousand invested in high end analyzers will chime in on how it can't work well but I've been using it for decades on numerous radios and for me and my needs it works great!
A Miracle Baby is the radio equivalent of earplugs. It's fine in strong-signal environments where a paper clip is adequate to get good reception, but is not appropriate for general use. It's like walking around wearing earplugs--appropriate in a room with noisy machines, but generally a dumb thing to do otherwise.

Most other antennas will give you 10-20dB more signal than a miracle baby, which is usually preferable.
 

iMONITOR

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Most other antennas will give you 10-20dB more signal than a miracle baby, which is usually preferable.
Those antennas you speak of is why so many people have difficulty with 800 MHz simulcast systems. In those instances the fewer antenna sites you receive the better. Not all situations call for a bigger higher gain antenna when in fact that's what contributing to the problem.

Like I said the CH-32 works great for me! Just because something does not work well for you does not make it a dumb thing for others to do if it works and solves their problem. Oh yea before you say "If you buy a SDS you won't have simulcast problems" we knew that already I have one. If someone can solve simucast problems on their less expensive scanner for $25 I'd say it's a very smart thing to do!
 

jonwienke

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Those antennas you speak of is why so many people have difficulty with 800 MHz simulcast systems.
No, it's because people are trying to use receivers not designed for simulcast to receive simulcast signals.

In those instances the fewer antenna sites you receive the better. Not all situations call for a bigger higher gain antenna when in fact that's what contributing to the problem.
The CH-32 is basically a fixed attenuator. IF it just happens to attenuate all but the strongest transmitter below the receiver's noise threshold, without doing the same for the entire signal, it can help. But that's only useful for reception at a fixed location, and is an unlikely scenario. It's far more likely that it will either attenuate the signal so much it's too weak to be received at all, or not attenuate enough to push the interfering transmitter(s) below the noise threshold. It's a total crapshoot, and the odds are not in your favor. A variable attenuator is more likely to work than any fixed attenuator.

Like I said the CH-32 works great for me! Just because something does not work well for you does not make it a dumb thing for others to do if it works and solves their problem. Oh yea before you say "If you buy a SDS you won't have simulcast problems" we knew that already I have one. If someone can solve simucast problems on their less expensive scanner for $25 I'd say it's a very smart thing to do!
It's not smart if the odds of success are less than 25%. Stupid simulcast antenna tricks fail more often than they succeed, are only useful in fixed locations, and bork reception for anything else you may want to monitor. Would you recommend a cancer treatment if it only didn't kill you 25% of the time?
 

trentbob

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It's actually fairly common to need washers or spacers between the antenna and radio to get SMA antennas to fit right. As to the rest of your comments, :rolleyes: ...
A Miracle Baby is the radio equivalent of earplugs. It's fine in strong-signal environments where a paper clip is adequate to get good reception, but is not appropriate for general use. It's like walking around wearing earplugs--appropriate in a room with noisy machines, but generally a dumb thing to do otherwise.

Most other antennas will give you 10-20dB more signal than a miracle baby, which is usually preferable.
Yes Jon, this is a conversation amongst very seasoned, experienced people who are familiar with the miracle baby for decades.

The whole point of the application suggested here was a desensitized, inefficient antenna. I did point out that even though it is designated a tri-band it really is best on 7 - 800 megahertz. In a strong system it works pretty good, in a simulcast distortion environment secondary to LSM it can be helpful.

Everyone here knows its inherent limitations and specific applications so it's tough to label anybody here dumb by using it.:p
 

iMONITOR

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Would you recommend a cancer treatment if it only didn't kill you 25% of the time?
Of course I wouldn't, I'm not a doctor nor am I discussing cancer. But for the record countless people have been successfully treated with alternative methods and survived cancer and that's what counts! Would you avoid it if it could save your life?
 

iMONITOR

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No, it's because people are trying to use receivers not designed for simulcast to receive simulcast signals.
In some cases that's all they can afford and if trentbob and myself pass along to others what works for us and it can possibly help them what's the harm in that? For many of us that's half the fun with our radio hobby, experimentation, trying different things that deviate from the norm and achieving success!
 

trentbob

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In some cases that's all they can afford and if trentbob and myself pass along to others what works for us and it can possibly help them what's the harm in that? For many of us that's half the fun with our radio hobby, experimentation, trying different things that deviate from the norm and achieving success!
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