Tech Tip: Adaptor for MTS/HT/XTS/STX Radios

Monty · Post by **Monty** » Thu Sep 23, 2004 11:04 pm

Hello:

Just a Tech Tip from my service bench:

I was just board fixing radios, and was not very
happy with a big Adaptor hanging out of the antenna
connector of the MTS / HT1000 / Visar Series of
radios when servicing them.

So, I got the idea about using a old Antenna
Base off of a 900 Mhz Antenna since most of
the Ant style Connectors fit flush with the bottom
of the Antenna Cavity and most adaptors have a
Small Ridge preventing the SMA style adaptors
from making a 100% good connection.

With a little effort, I was able to recover the
entire Connector off the base of one of the
molded heliflex 900 Mhz Antenna, and to my
surprise, I found the Antenna wire was soldered
to the center pin!

So, I took the old Molded heliflex antenna
apart, used some Teflon Cable ( since the size
of the Center Conductor had to be close
enough to fit on the Center pin of the SMA
Connector.

Soldered everything in place, used a Crimp Support
and some heat shrink, and ended up with a very
nice tight fit.

Then, I place a SMA Male Connector on the other end, did
much the same, added a SMA Female to BNC Female
Adaptor, and came up with a super nice test cable.

Took about 45 min, and I tossed the other adaptor aside
since I missplaced it so often.

The Cable is not obtrusive, and works great so I thought
it would be a good Tech Tip for those who have a OLD
800 / 900 Mhz Portable Antenna and you can get some
more milage out of it so long as you are into making
detailed Power Adjustments or Receiver Sensitivity
measurements.

It also alows full testing of the Antenna base since you
can apply pressure on it while in transmitt to see if there
are any intermittent conditions.

Hope you can use the information.

Monty

n3kvp · Post by **n3kvp** » Fri Sep 24, 2004 6:31 am

Are you going to be selling these??

Butch

Monty · Post by **Monty** » Fri Sep 24, 2004 11:05 am

HI Butch:

Well, its not the easist cable I have made, but
if you have a need, please email me and its
possible I could consider making a few.

The one I made with the SMA Connector is expensive
due to the connectors and the adaptor, I could however
consider just using a Coaxial BNC Jack, and not use the
SMA Plug and Jack....Only reason I did that is this was
a first generation adaptor cable I made.

I just got tired of the old clunky type N Female to the Female
SMA Adaptor, and I wanted a smaller Teflon Cable to work with.

If I am going to build some, I always like to
build 4 ~ 5 of them at a time as is saves on the
asprin...

If there are more than a few, perhaps I will make some
this weekend....

Monty
[email protected]

Post by **wavetar** » Fri Sep 24, 2004 11:59 am

You were using an N-female to SMA adaptor? No wonder you were sick of it. Why not just use the Motorola recommended BNC to SMA adaptor? Part# 5880348B33

Todd

Monty · Post by **Monty** » Fri Sep 24, 2004 2:04 pm

You were using an N-female to SMA adaptor? No wonder you were sick of it. Why not just use the Motorola recommended BNC to SMA adaptor? Part# 5880348B33

Hi Todd:

YES ! I have used that adaptor !, however I have also managed
to loose 3 of them ! I have even lost some of the larger ones
too !

And, by the time one has to pay for the adaptor ( about 25.00 )
and shipping, if one missplaces them, it can be a expensive
30.00 / 32.00 lesson if it gets lost.

Hopefully the Cable ( that is white ) will not be a easy to
missplace or loose.

Now I just have to get the other techs in the shop to
leave it alone ! It was not 2 hours this morning that one
of my helpers wanted to use it. I told him to make his
own !

I had to get a number of small prescription bottles to
start storing all these dam adaptors since almost each
portable uses its own adaptor.

EEgads

So, with that in mind, along with having to deal with my
normal set of Test Cables made out of RG-223/U and RG-142BU
I was not happy having to deal with the stiffer cables, larger
adaptor all the time.

I was a bit sneaky, in that I used the Cable from a 800 Mhz
Antenna and the cable is about 1/2 the size and much easier
to handle when its connected to the Radio.

With the smaller cable, its much easier to navigate using
the buttons on the top and front.

So, there is a application to meet anyones needs.....

Monty

Zero dbm · Post by **Zero dbm** » Fri Sep 24, 2004 3:13 pm

I have experienced this too. I just, carefully, ground down that ridge to make it close to flush with the inner teflon. Perfect working order.

Cheers all

Monty · Post by **Monty** » Fri Sep 24, 2004 5:16 pm

I have experienced this too. I just, carefully, ground down that ridge to make it close to flush with the inner teflon. Perfect working order.

Hi:

Just for information:

The total Depth of the SMA Connector in the HT1000 Series
Radio is .250 in. AND the very Top of the pin sits .140 in
below the surface. ( A difference of .110 in. )

The lenght of most of these adaptors total .250 and
the first part of the contact is .075 in below the edge.

As a result, if you use a Adaptor ( as in the photos )
the center of the Pin only goes in about 1/3 of the
way so there is not really a 100% coverage of the
pin on the inside of the radio.

What happens, is that even if you " Trim " the edge off most
of these SMA Adaptors, you still will not have enough lenght
to have the center pin mate with the connector in the radio
and this is due to the top part of the SMA Connector head.

However, there are some adaptors that are longer than .250in
and the above does not apply to them. But most SMA Connectors
are only .250 in total thread lenght.

The one in the photo above to the very left is about .500 in long!
and those can be Trimmed if you are carfull about the threads.

Its sorta like having a PL-259 pluged in [ 1/3 way ]....Still
will work, but unfortunitly unless you have one of the Adaptors
with 1/2 " in lenght, it will not seat well, and if you try to trim
it flush with the surface, the insulator will become loose, so
if you should try this, I would not recommend going all the way
down to the surface of the pin....leave a little bit to help hold
the insulator in place.

Enough for it to work, but one still should be aware of the
total thread lenght depending on the adaptor being modified.

Monty

Post by **wavetar** » Fri Sep 24, 2004 6:42 pm

Monty wrote:
You were using an N-female to SMA adaptor? No wonder you were sick of it. Why not just use the Motorola recommended BNC to SMA adaptor? Part# 5880348B33

Hi Todd:

YES ! I have used that adaptor !, however I have also managed
to loose 3 of them ! I have even lost some of the larger ones
too !

Monty

Ah, I see. I have lost one myself....of course, I have lost much larger things as well. Nice looking cable though.

Todd

kcbooboo · Post by **kcbooboo** » Sat Sep 25, 2004 4:15 am

I found an adapter at http://www.hdcom.com that's a BNC female to SMA female. It fits GTX portables, but only screws in a couple of turns. However, it does work, and costs quite a bit less than the equivalent Motorola part.

"RFB-1142-4 BNC Female to SMA (Motorola) Female Use with Motorola Cellular $3.29"

Note that they have several different RFB-1142 parts - I bought one of each. Only the -4 part fits into the GTX portable's antenna adapter socket.

I'm sure this same company could make the cable that Monty did, but they tend to start around $30.

Bob M.

nmfire10 · Post by **nmfire10** » Sat Sep 25, 2004 5:06 am

This may sound stupid but couldn't I just take my dremel and "remove" that ridge on the normal SMA adaptor? It would still work on other radios and would then fit on the Jedi, etc portables.

Monty · Post by **Monty** » Sat Sep 25, 2004 9:30 am

This may sound stupid but couldn't I just take my dremel and "remove" that ridge on the normal SMA adaptor? It would still work on other radios and would then fit on the Jedi, etc portables.

This has already be covered !

The big reason is that most adaptors have a Thread lenght
of only [ .250 in ] and the Contact is [ Recessed ] below the
ridge.

The issue is the Adaptors " Just barely " make contact with
the center pin, regardless if you trim the ridge off and a adaptor
that has a Total Thread Lenght of only 1/4 " !

The "Only Exdception" is where the Thread Lenght is like a
1/2 in, and then it is possible to file down the Ridge. BUT
one has to be carful about triming down to far and the thread
pitch may be off a little.

Trim to much off and the Insulator will fall out, trim it uneven,
and you could compromise the Thread Pitch and damage the
Antenna Cavity Threads ; ( meaning a uneven Fit )

If you ever have done much RF Work, its very important to
have a firm Fit to prevent any intermittent conditions and thus
a possible RF failure.

Power Amps in MTS2000's / HT1000's are " Soldered to " the Main
PC board and are almost impossible to replace unless you have the
proper tools......

So, one needss to be very careful when dealing with this area
of the radio.

Hence the reason ( in most cases ) for the requirement of the
" Mototola Service Adaptor ) and a Adaptor Service Cable, or
one can build something a little smaller which is more easy to
work with and will fit the Antenna Cavity 100% just like the
Antenna does.

As metioned above, you may chose whichever suits you best.

PS: I have already been requested to make some for
forum members, and I have reach the limit for this weekend.

Should you desire the cable route, I will be happy to give
details how you can build your own, but I just do not have
anymore materials to build more....

You are " on your own " there !

Monty

JohnWayne · Post by **JohnWayne** » Sat Sep 25, 2004 12:40 pm

Just an FYI, those RFB-1142-4 adapters work perfectly on the Motorola radios that use the special SMA connector. They seat fully and make excellent contact with the connector. The RFB-1142 (no -4) doesn’t work so well, and that must be what Monty is referring to.

You can get your very own by clicking here. Note: the picture on there is of the RFB-1142, the RFB-1142-4 does not have the "shroud" on the SMA side. I can post a picture of the actual part if someone wants.

Let me know if you have any questions.

Thanks,
Jeff

Monty · Post by **Monty** » Sat Sep 25, 2004 2:20 pm

I can post a picture of the actual part if someone wants.

I went to the site where the add was for the connector
you were speaking of, and enlarged the photo, and the
one in the photo shows the same ridge and is the one
featured in the add.

It can be seen @

http://metro-tech.net/pics/mts_adp.jpg

However:

I am sure many may be interested in the Close Up
of a alternate photo .If it seats all the way down to
the Bottom that would be a PLUS, and I also would
like to know if the Center Pin may be [ Gold Plated ]
That to would be a Plus.=======================================
If its the same one from RF Industries, there still
could be a issue about the Depth.

It may go all the way in, BUT the one I have still has that
ridge by about a 1/10 of a inch and will NOT allow
full coverage of the Pin inside the radio.

I have one of the RF Industires Adaptors you mention
and it still has that leading Ridge.

The one I have is a RFA-3413

Although the above connector may work, it was
designed for a SMA Style Connector, and Not the Radio....

Coverage of the inside of the Pin is only about 1/3 of the
total amount.....

If you use the Motorola Adaptor OR the Cable approch, its covered 100% of the way !

======================================

What happens with these style adaptors is one may still
have to deal ( with a Service Cable made out of RG223/U ,
RG-142BU or worse case RG-58A/U ) and makes the
cable / Adaptor hard to deal with.

MS

JohnWayne · Post by **JohnWayne** » Sat Sep 25, 2004 6:15 pm

Monty said:

I went to the site where the add was for the connector
you were speaking of, and enlarged the photo, and the
one in the photo shows the same ridge

Yes, that is why I said in my original post:

Note: the picture on there is of the RFB-1142, the RFB-1142-4 does not have the "shroud" on the SMA side.

Monty said:

I have one of the RF Industires Adaptors you mention
and it still has that leading Ridge.
The one I have is a RFA-3413

RFA-3413 is NOT the part that I mention. The part that I mention is RFB-1142-4. I don't even see RFA-3413 in any of my RF Industries catalogs.

I just took a few pictures of the RFB-1142-4 so that you can see it. As you can see, there is no ridge, and the center pin is gold plated:

http://www.waltel.com/rfb11424-3.jpg

This is the exact adapter that I have used hundreds of times to service radios with the "SF" (special Motorola SMA style) antenna connector. It works like a champ every time. I just attach whatever service cable that I need directly to it. It just works.

Jeff

Monty · Post by **Monty** » Sat Sep 25, 2004 7:26 pm

Hi Jeff:

Looks like a "Ideal Adaptor" and it also has a
" Gold Plated " Insert ! unlike the older Plated style
in a early version I have seen.

======================================

You should consider making changes in the add since
the discription it shows the other style connector and
not the one above. I sure its just a oversight.

I was aware of it, but some members may not be aware
that there are [ 2 ] different style of adaptors that you offer.
======================================

Add a Good BNC Male to BNC Male Service Cable
and it sure beats the " Clunker " style Type N type
Adaptors.

The following photo should show what options one
may have when Servicing these portables.

Thanks for your information, and I am sure it will be
helpfull to many as some try and use that connector
with the Ridge, and truly they are a little problematic.

Play it SAFE, use the correct cable or adaptor for the job!

Monty

Lord Windeshmere · Post by **Lord Windeshmere** » Sat Oct 09, 2004 8:08 am

I'm surprised no one takes apart a Jedi, for instance, antenna and solder a cable with a BNC at the other end. Has anyone tried this?

ExKa|iBuR · Post by **ExKa|iBuR** » Sat Oct 09, 2004 8:47 am

I had looked into how feasible it would be to replace the SMA or wahtever it is on a Jedi with a BNC connecter to make it easy to swap between coax and antenna. It doesn't look like it would be that difficult, problem is me finding the time

-M

Lord Windeshmere · Post by **Lord Windeshmere** » Sat Oct 09, 2004 10:11 am

Definitely could be done. I don't have any handy to look at, but is a female BNC bigger than an SMA?

I'm going to rip apart an old Jedi antenna to see about using the male SMA for a test cable. I finally got myself a service monitor, R2001D/HS, so I'm all about it and test cables right now.

sglass · Post by **sglass** » Sat Oct 09, 2004 11:16 am

bnc huh

ok, sounds like a useless project to take up my spare time

might as well make use of the machine shop while I still have access

I have a backing I can sacrifice too.

Seth

maybe tnc though

tnc is lower loss right?

Lord Windeshmere · Post by **Lord Windeshmere** » Sat Oct 09, 2004 6:50 pm

The TNC was designed as a threaded version of the BNC. You can use a TNC for 0-11GHz. If you really wanted something other than SMA I'd go with the TNC over BNC. IMO I wouldn't putz around with the antenna connector on my portable. SMA works and fits the radio's housing, obviously, perfectly.

sglass · Post by **sglass** » Sat Oct 09, 2004 6:54 pm

Lord Windeshmere wrote:The TNC was designed as a threaded version of the BNC. You can use a TNC for 0-11GHz. If you really wanted something other than SMA I'd go with the TNC over BNC. IMO I wouldn't putz around with the antenna connector on my portable. SMA works and fits the radio's housing, obviously, perfectly.

oh this is just for shits and giggles

Lord Windeshmere · Post by **Lord Windeshmere** » Sat Oct 09, 2004 6:57 pm

I hear you. If you get one together shoot up a pic.