Motorola HT1000 Antenna Question VHF and UHF Differance

troymelina · Post by **troymelina** » Mon Jan 24, 2005 1:35 pm

The question I have is:I tried something odd by putting a VHF antenna on a UHF radio and seems to work great!!!

The reason I had done this is because the (2) radio's were making a crackling sound on TX because of the UHF antenna's.

Don't know why.But when I put the VHF antenna's on the sound went away.....Why is that??

Is there something wrong with the UHF antenna's And does it cause any harm to use VHF antenna's on a UHF radio?thanks

RadioSouth · Post by **RadioSouth** » Mon Jan 24, 2005 3:08 pm

You don't want to TX with an improper antenna otherwise you'll be on the market for a new RF amp.

troymelina · Post by **troymelina** » Mon Jan 24, 2005 3:16 pm

Hi Radiosouth and thanks for the info but why would the UHF antenna's make a crackling noise but the VHF antenna's won't....

Is there something wrong with the UHF antenna's?thanks again Troy

RadioSouth · Post by **RadioSouth** » Mon Jan 24, 2005 3:32 pm

Would suspect either the UHF antenna has a break in it somewhere or doesn't quite fit, this an aftermarket antenna and what radio type we talking ?

troymelina · Post by **troymelina** » Mon Jan 24, 2005 3:38 pm

The UHF antenna is a Motorola Original

RadioSouth · Post by **RadioSouth** » Mon Jan 24, 2005 3:39 pm

What type radios?

troymelina · Post by **troymelina** » Mon Jan 24, 2005 3:41 pm

Motorola HT1000 UHF radio's model# H01SDC9AA3BN

troymelina · Post by **troymelina** » Mon Jan 24, 2005 3:54 pm

Also is there away to look at the boards when you take the front case off to visually look for numbers or codes to tell if it's a UHF or VHF board,just wondering if someone did a change on the housing or something on the inside of the radio.thanks again

RadioSouth · Post by **RadioSouth** » Mon Jan 24, 2005 4:02 pm

The only other things that come to mind is the antenna connector on the radio, the VHF antenna might be holding different 'traction' on it than the UHF and might make a difference if the connector has loosened up (A version radios were known for this loose antenna connector issue). Also some of the UHF HT1000's develop a crackling problem and Motorola has come out with a microphonics kit to address this but the antenna wouldn't matter, this relates to grounding issues on the boards and frame. From my perspective it boils down to bad antenna, bad antenna connector on radio or microphonics. That about covers the mechanical possibilities, could also be an electronic problem. Board #'s can be found in the archives but if it's TXing on UHF it wouldn't have a VHF board.

troymelina · Post by **troymelina** » Mon Jan 24, 2005 4:07 pm

Thanks for all the information RadioSouth. Very Much Appreciated,Troy

troymelina · Post by **troymelina** » Mon Jan 24, 2005 4:08 pm

Also is there away to look at the boards when you take the front case off to visually look for numbers or codes to tell if it's a UHF or VHF board,just wondering if someone did a change on the housing or something on the inside of the radio.thanks again

thebigphish · Post by **thebigphish** » Mon Jan 24, 2005 4:50 pm

troymelina wrote:Is there something wrong with the UHF antenna's And does it cause any harm to use VHF antenna's on a UHF radio?thanks

you will smoke the RF deck from transmitting into a mistuned antenna. just like RadioSouth said, start looking for a RF deck to replace your original...

troymelina · Post by **troymelina** » Mon Jan 24, 2005 6:27 pm

Still looking for the question that I have :::Is there away to look at the boards when you take the front case off to visually look for numbers or codes to tell if it's a UHF or VHF boards,just wondering if someone did a change on the housing or something on the inside of the radio.thanks again

Keygun · Post by **Keygun** » Tue Jan 25, 2005 3:11 am

troymelina wrote:Still looking for the question that I have :::Is there away to look at the boards when you take the front case off to visually look for numbers or codes to tell if it's a UHF or VHF boards,just wondering if someone did a change on the housing or something on the inside of the radio.thanks again

No, you have to remove the inner shield, to read the RF-Boards model-number.

Keygun

Keygun · Post by **Keygun** » Tue Jan 25, 2005 3:17 am

troymelina wrote:The question I have is:I tried something odd by putting a VHF antenna on a UHF radio and seems to work great!!!

The reason I had done this is because the (2) radio's were making a crackling sound on TX because of the UHF antenna's.

Don't know why.But when I put the VHF antenna's on the sound went away.....Why is that??

Is there something wrong with the UHF antenna's And does it cause any harm to use VHF antenna's on a UHF radio?thanks

Another thing: Jedi`s (and also Sabers) are know to develop this crackling noise. This is caused by contact problems between the inner shield (which covers controller and RF-board), and the solder-pads of the RF-board ground. When RF-current is creeping around inside the radio (and it always will, during tx-ing), this bad contact produces the crackling noises. You can reproduce it by pressing the radios front. When using the wrong type of antenna, there is is not much RF on the way, due the extreme mismatch - so the crackling is gone (or at least less heavy).

Keygun

kato56 · Post by **kato56** » Tue Jan 25, 2005 11:11 am

I have this problem on my A7 MT2000. How can I improve the contact between the inner shield and the ground pads?

Thanks

Keygun wrote:
troymelina wrote:The question I have is:I tried something odd by putting a VHF antenna on a UHF radio and seems to work great!!!

The reason I had done this is because the (2) radio's were making a crackling sound on TX because of the UHF antenna's.

Don't know why.But when I put the VHF antenna's on the sound went away.....Why is that??

Is there something wrong with the UHF antenna's And does it cause any harm to use VHF antenna's on a UHF radio?thanks

Another thing: Jedi`s (and also Sabers) are know to develop this crackling noise. This is caused by contact problems between the inner shield (which covers controller and RF-board), and the solder-pads of the RF-board ground. When RF-current is creeping around inside the radio (and it always will, during tx-ing), this bad contact produces the crackling noises. You can reproduce it by pressing the radios front. When using the wrong type of antenna, there is is not much RF on the way, due the extreme mismatch - so the crackling is gone (or at least less heavy).

Keygun

MotoVio · Post by **MotoVio** » Tue Jan 25, 2005 4:22 pm

Order the JEDI MICROPHONICS KIT p/n: REX4465A (Addresses the contact issue)

Not sure if It's a do-it-your-selfer or you'd have to have the nearest MSS or the Depot do it, I've never had to deal with it.

Vio

troymelina · Post by **troymelina** » Tue Jan 25, 2005 6:51 pm

I would like to thank everyone who responded to the questions that I had.Everyone was helpful,thanks again Troy D

Keygun · Post by **Keygun** » Wed Jan 26, 2005 1:12 pm

kato56 wrote:I have this problem on my A7 MT2000. How can I improve the contact between the inner shield and the ground pads?

Some technicians solve the problem with soldering shield and ground-pads together. Its the simplest, but not the smartest solution. Better is to remove the shield, clean the ground-pads with alcohol. If necessary, carefully put an thin layer of "fresh" solder on them, clean again with alcohol (to remove the solder flux) and put the shield back. With a little luck, the noise is gone.

Keygun

Tony Soprano · Post by **Tony Soprano** » Wed Jan 26, 2005 1:28 pm

Keygun wrote:
kato56 wrote:I have this problem on my A7 MT2000. How can I improve the contact between the inner shield and the ground pads?

Some technicians solve the problem with soldering shield and ground-pads together. Its the simplest, but not the smartest solution. Better is to remove the shield, clean the ground-pads with alcohol. If necessary, carefully put an thin layer of "fresh" solder on them, clean again with alcohol (to remove the solder flux) and put the shield back. With a little luck, the noise is gone.

Keygun

Motorola SRN-1202D dated June 1997 but up-issued January 2000 recommends the method of soldering the shields together. This method works best in my experience, and beats the old conductive tape pads hands down. And you can do about ten radios with this method for every one radio that you remove and re-solder the shields on.

Will · Post by **Will** » Wed Jan 26, 2005 2:57 pm

Would you be able to post the text from that SRN update, I think it may be helpfull.

I would not anyone going wild with a soldering iron.

Rayjk110 · Post by **Rayjk110** » Wed Jan 26, 2005 3:04 pm

I've had that 'crackling' noise problem with my UHF Visar, but I think that's just the way Visar's are, since it happens on all of mine. I think I've read that somewhere on Batboards....
-Ray

RadioSouth · Post by **RadioSouth** » Wed Jan 26, 2005 3:39 pm

I believe the SRN that Tony mentions covers the Visar as well. Applies to UHF models only.

Tony Soprano · Post by **Tony Soprano** » Thu Jan 27, 2005 6:01 am

All:

Here is the text of SRN-1202D. There are also pictures on the original PDF that this came on, if anyone is interested in an original copy, please PM me.

THIS BULLETIN SUPERSEDES PREVIOUS RELEASE - SRN1202A/B/C
SRN - 1202D
APC - 355, 402, 432,466, 511
Date: June 1997 : Up Issued 1/00
Date Extension Only
Memo To: SRN Mailing List
Deadline: Dec. 31, 2001
From: Subscribers Product Groups/Plantation, FL
Subject: Transmit Microphonics on HT1000, JT1000, MTX838, MT2000 & MTS2000 UHF Radios
Symptoms:
A small percentage of HT1000, JT1000, MTX838, MT2000, & MTS2000 UHF radios may exhibit transmit microphonics, where
one of the following occurs:
1) Popping, crackling, or snapping noise at times making audio communication
unintelligible in the receiving radio.
2) Transmitting radio may be transmitting distorted DTMF tones.
Potential Problem Radios:
HT1000, JT1000, MTX838, MT2000 & MTS2000 UHF band radios manufactured between November of 1995 through May of
1997 Serial numbers denoted by: xxxAVWxxxx to xxxAXKxxxx
HT1000 model numbers: H01RDC..., H01SDC......N
JT1000 model numbers: H01RDH..., H01SDH.....N
MTX838 model numbers: H01RDC..., H01RDD..., & H01RDH.....N
MT2000 model numbers: H01RDx...., H01SDx......N
MTS2000 model numbers: H01RDx9PW1xN or H01SDx9PW1xN
Cause:
Some of the above radios may have been manufactured with inadequate / unequal internal grounds and shield flexibility.
Required Material:
REX4465A, material in this kit is listed below.
Part Number Description
1405307X07 Kapton Tape
2605891U03 Front Shield
NTN7087A Control Flex
7505922Z01 Thermal Pad
1185821A01 Copper Tape
SRN 1202D
7505393N33 Shock Pad
Corrective Action:
Remove any solder on the RF Printed Circuit ground tab by coil L11. Remove the kapton tape from the strip, part number
1405307X07 and trim it to size approximately .3"x.2". The tape on the strip is .5" x .25" before trimming. When placing
the tape on the printed circuit board make sure there is a sufficient amount to go over the tab to insulate it from the
projection of the front shield. See figure 1.
1.
Page 1 of 3
Remove all conductive pads that may have been placed on the RF board, part numbers 7505870Z01,
7505870Z02, or 7505870Z03. (These pads were added in some radios per SRN 1202.)
2. Solder shield ME1 to ME2. See figure 2. A minimum of three solder bridges should be used. The solder should bridge the gap
between the shields but not project above the top of the shields on the PCB. Solder shields ME6 and ME7 together in the same
manner. See figure 3.
3. Inspect the surface of the PA, U105, where it rests on the casting. See figure 4. This casting surface acts as a heat sink and may
be covered by thermal grease or a thermal pad which must be removed for inspection. The exposed PA surface must be flat with
no evidence of solder build up along the entire surface. The build up will look like bumps or blisters which may cause the board to
rock. Remove any build up with a sharp blade or similar tool. Do not leave burrs. (NOTE: DO NOT REMOVE THE PA TO
PERFORM THIS STEP.)
4. If the portable was shipped with thermal grease or a thermal pad replace with the thermal pad provided in the kit, part number
7505922Z01.
5. Replace the front shield with part number 2605891U03. A new control flex, part number NTN7087A, will have to be attached
to this shield. When attaching the new shield pay special attention that the shield tabs are properly engaged into the rear casting.
The lance of the tabs should be seated into the rear casting as deeply as possible. A small screwdriver should be used to ensure
proper seating. See figure 5.
6. HT1000 ONLY: Apply a piece of copper tape, part number 1185821A01, across the silver ground contact on the control flex
and main shield. Place a shock pad, part number 7505393N33, over the copper tape above the main shield to prevent contact with
the front cover.
Parts and $45 labor is authorized by warranty. Contact your local Motorola Authorized Service Representative to arrange for this
modification. Agency Approved product should follow the guidelines for repairs and service.
SRN 1202D
SRN 1202D