Re: Duplexer for amateur 70-cm band
Chris, you are welcome to email me for details.
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Regards, Karl Shoemaker
To contact me, please visit SRG's web site at?
for the current email address.
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Identify his module because I can’t.
Looking at spare module for the mtr2000 and came across this module and I have no idea what band it is for. 
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Re: VHF Duplexer Identification
4062 is 6 cavities.? 4060 is 4 cavities.? Is the height 34.5 inches? ?
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From: [email protected] <[email protected]> On Behalf Of Jeff Acree via groups.io
Sent: Wednesday, April 9, 2025 9:40 PM
To: [email protected]
Subject: [repeater-builder] VHF Duplexer Identification? Please take a look at the attached pictures and see if you can identify the duplexer.? it seems like it may be something along the lines of a Decibel Products DB4062-WOC-B.? In the Ham VHF repeater band, they seem to have about 1 dB per channel of passband insertion loss and about 75 dB of rejection in the notches.? Thoughts?
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VHF Duplexer Identification
Friends,
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Please take a look at the attached pictures and see if you can identify the duplexer.? it seems like it may be something along the lines of a Decibel Products DB4062-WOC-B.? In the Ham VHF repeater band, they seem to have about 1 dB per channel of passband insertion loss and about 75 dB of rejection in the notches.? Thoughts?
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Thanks!
Jeff KC8VFN
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Anybody have any knowledge or documents to add to the Helper Instruments page ?
I recently had the need to do some research on Helper Instruments and locate a schematic.?
I ended up overhauling the page at Repeater-Builder.
Does anyone know what Bill Detweiler's ham callsign was??
It's undoubtedly been reissued...?? Neither the ARRL or the RCA have that...
Does anyone know who the rest of the Helper people were? Or what happened to them?
Maybe you have an old business card in the back of a desk drawer?
If anyone has the missing applications notes it would be nice if we could offer them for download.
If all you have is a paper copy we'd be happy to scan it and return it.
The missing ones are:
Everything you need to know about SINAD
Line Measurements Speed Control System Troubleshooting
What the Modulation Monitor Has Missed
Troubleshooting With Your Power Supply
R.F. Voltmeters
Thanks in advance
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The front end helicals need to be retuned for below 450 MHz receive. Something like a 10MHz spread if you tune for flat top response as Kenwood suggests in the manual (see the R-B archived TK890(H) service manual. For just about 442- 450 MHz repeater receive frequency, tune the helicals for peak response on the repeat receive frequency for best sensitivity.
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John
On 04/09/2025 5:27 PM EDT Mike Besemer - WM4B via groups.io <mwbesemer@...> wrote:
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Hmmmm… sound more like an alignment than a ‘tweak’.?
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Mike
WM4B
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On Wed, Apr 9, 2025, 14:53 Hudson, John@CalOES via <john.hudson=[email protected]> wrote:
In what way does the TK-890’s need tweaking??
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This Message is From an External Sender
This message came from outside your organization.
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TK-890's aren't bad, but some need slight tweaking
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I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
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The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn
WARNING: Do not click links or attachments unless you recognize the sender and know the email is safe.
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Hmmmm… sound more like an alignment than a ‘tweak’.? ? Mike WM4B ?
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From: [email protected] <[email protected]> On Behalf Of K6LOR.com via groups.io
Sent: Wednesday, April 9, 2025 5:03 PM
To: [email protected]
Subject: Re: [repeater-builder] UHF mobiles? ? On Wed, Apr 9, 2025, 14:53 Hudson, John@CalOES via <john.hudson=[email protected]> wrote: In what way does the TK-890’s need tweaking?? ? ? This Message is From an External Sender
This message came from outside your organization. ? TK-890's aren't bad, but some need slight tweaking ? I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
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The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn WARNING: Do not click links or attachments unless you recognize the sender and know the email is safe. ?
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On Wed, Apr 9, 2025, 14:53 Hudson, John@CalOES via <john.hudson= [email protected]> wrote:
In what way does the TK-890’s need tweaking??
?
?
This Message is From an External Sender
This message came from outside your organization.
?
TK-890's aren't bad, but some need slight tweaking
?
I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
--
The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the
years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn
WARNING: Do not click links or attachments unless you recognize the sender and know the email is safe.
?
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In what way does the TK-890’s need tweaking??
?
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From: [email protected] <[email protected]>
On Behalf Of John N3XKD via groups.io
Sent: Tuesday, April 8, 2025 6:37 PM
To: [email protected]
Subject: Re: [repeater-builder] UHF mobiles
?
This Message is From an External Sender
This message came from outside your organization.
?
TK-890's aren't bad, but some need slight tweaking
?
I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
--
The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the
years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn
WARNING: Do not click links or attachments unless you recognize the sender and know the email is safe.
?
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Such a device exists.? Its commonly referred to as a Thumper. Basically
it is a high voltage pulse that causes the fault to break down.? I
rented one on 2 occasions to locate a underground fault in a underground
feeder to a microwave site.? The package also included an ultrasonic
detector that was used to pinpoint the exact location of the fault.?
Once we got close you could actually hear and feel the arc generated by
the thumper.? In both instances we contracted with a HV splicing company
to do the actual repair. There is also a mode called a burn down that
uses a high voltage DC to cause the fault to get bad enough to locate.?
The book that comes with the Thumper lists the various dielectric
constants for the various forms of cables, very similar to the velocity
factor of coax cables.
The actual splice kits have the shrink tubing to splice the power
conductor, the dielectric insulator and the outside jacket called the
semiconductor to prevent a point failure due to corona point discharge.?
Generally you have to use 2 splice kits and a short section of
compatible feeder to make up for the damaged section.
Jack K6YC
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John – can you elaborate? ? ?
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From: [email protected] <[email protected]> On Behalf Of John N3XKD via groups.io
Sent: Tuesday, April 8, 2025 9:37 PM
To: [email protected]
Subject: Re: [repeater-builder] UHF mobiles? TK-890's aren't bad, but some need slight tweaking ? I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
--
The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn
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Re: TX Board for Motorola XPR8300 Repeater?
I did the same with great success. Also added a ~2" muffin fan to the additional tx deck heatsink. Been working well through thousands of daily nets for close to 10 years.
Ross? kc7rjk
On Apr 8, 2025 1:38 PM, "Chris Boone WB5ITT via groups.io" <setxtelecom@...> wrote: Swap the TX and RX decks...replace the piss poor fabric under the heatsink on the TX..use artic silver....run power lower at 30 instead of 40watts ..
Chris WB5ITT
I am resurrecting an XPR8300. The TX board is scorched.?
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Board #:
MOTOTRBO U1-HP
8486777Z14-C
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UHF Ham Range
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Does anyone have a parted-out XPR8300 willing to sell the TX board to me?
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The poor heat-dissipation design makes this a seemingly common ailment.
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Private message me.
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Thanks,
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Steve, N9ATO
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TK-890's aren't bad, but some need slight tweaking
I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
-- John Kreno
The line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains … an unuprooted small corner of evil. - Aleksandr Solzhenitsyn
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Follow up on KMC 35 Mic Mod for TKX90 Radios
For anyone not reading our original post a little background. The repeater-builder article on the TK690H mentioned that the black KMC35 mic gave better sounding audio than the OEM grey KMC27 mic supplied with the radio. This is noticeably the case, but there seemed to me that a little more highs would be an improvement even on the KMC35 mike replacement, which is the OEM mike supplied with the TK8180 and some other Kenwood mobiles. Therefore I removed chip cap C10 on the mic pc board which works as a low level low pass filter in the 600 ohm mic input to the radio to partially cut off above about 2200-2500 cps. The result was a somewhat improvement in passing some more speech highs, with no noticeable effect on mike lows, so probably? worth removing 0.068 uF C10.? The comment was made that that should not be necessary as audio was quite good with the KMC35 mike as stock. Then I realized that the TK8180 audio input response is flat to 2800 cps, but only to about 2200-2500 cps on the TK690H? radios tested.?
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John
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I have a Harris XG-75M that does 440-512 stock. Got it off eBay for about $175. Excellent radio with lots of features.?
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I've had good luck with Icom 6061?
Mike Ka2ndw
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On Tue, April 8, 2025 5:38
pm, Chad Nelson wrote:
Hi,
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Does anyone know what
version 2 UHF radios in the commercial line will operate
440-470 straight through without retuning?
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I have the TK 8180 which
works great in that range, the TK 8302 needs tweaking
every couple of MHz.
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Interested to know what
other radios will do this that have a front mounted
speaker?
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~Thanks,
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Chad
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Hi, ? Does anyone know what version 2 UHF radios in the commercial line will operate 440-470 straight through without retuning? ? I have the TK 8180 which works great in that range, the TK 8302 needs tweaking every couple of MHz. ? Interested to know what other radios will do this that have a front mounted speaker? ? ~Thanks, ? Chad
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Re: Duplexer for amateur 70-cm band
Yep...I have several myself...I can part with one if need be
Chris WB5ITT
If you can make it to Dayton in May there will be lots of those duplexers there cheap. Last few I bought were under $50 and they work fine.?
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Re: Improving selectivity on a reciver
The schematic for the receiver in question shows a single broad band pass filter before the FET 1st amplifier then a three section helical resonator after that. Not a very good design which would rely on the duplexer band pass to protect the FET from overload, generating IMD, etc. Depending on the duplexer used a single 1/4 wave cavity filter ahead of the receiver module would go a long way to reduce the repeater transmitter or out of band signals from degrading receive.?
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Re: Duplexer for amateur 70-cm band
If you can make it to Dayton in May there will be lots of those duplexers there cheap. Last few I bought were under $50 and they work fine.?
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Karl Shoemaker
Mike Besemer - WM4B
Hudson, John@CalOES
Chris Boone WB5ITT