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Re: UHF Repeater Input Frequency Issues
On Thu, Apr 3, 2025 at 06:49 PM, Matt wrote:
Thanks.? I come from the CATV world prior to ham radio.? The splitter terminology is very familiar, but every little corner of the RF world uses just slightly different language at times.? Was just checking.? ? I wouldn't have guessed that a preselector was a bandpass instead of an active device.? ? Thanks for all the great info folks.? We're on the right track now. |
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Re: Capacitors in DB4332B and DB4333B
开云体育Mike:Thank you for your emails. I agree it would be great if the capacitors at 850 Mhz were adjusted to something less than half of their range, I could just install the same size coils as in the 450 Mhz LPF and retune the capacitors. Looking at an old 1994 DB Catalog, the curves for the VHF, UHF, and 800 Mhz LPF's are identical. The 800 Mhz LPFs' are not in the 1993 Db Catalog. I did considered padding the capacitors if their values were different. I assumed Q of the circuit would change with the size of the capacitor and that would affect the response of the low pass circuit.? I can not see any component identification on the capacitors in either LPF that shows their manufacturer or value. Just looking, they kind of look like Johanson. I have pictures inside both of the LPFs. I have a capacitance meter with tweezer type probes. It was difficult to get a consistent readings. Besides, since I am not unsoldering the coils, I am actually measuring some overall capacitance value for all four of the capacitors connected in parallel which I expect would not be affected by the inductances of the coils because the measurement frequency is pretty low. I can't say it is that accurate since it is not a very expensive capacitance meter.? It did read something. I was just hoping that someone might have replaced a capacitor after a lightning strike or something similar, and knew the value. I may just start by reproducing the UHF coils and install them in the 850 Mhz LPF, then use the spectrum analyzer and see how low I can bring the knee of the filter and pad it if I can't reach 450 Mhz.? The UHF coils look like they are expanded and mashed as part of the tuning. Micheal Salem ? On 4/3/2025 11:41 PM, Mike via
groups.io wrote:
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Re: Where did db Products go?
DB Products was bought out by Comscope along time ago. Les Keegan N4LPK?
On Thursday, April 3, 2025 at 07:02:40 PM EDT, Karl Shoemaker via groups.io <srg734@...> wrote:
In my research I found conflicting information this past year or more.??? Did db Products get bought by db spectra or Comscope?
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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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Re: UHF Repeater Input Frequency Issues
开云体育A preselector is simply a band pass filter. A splitter is….. a splitter. ? Matt AL0R ? From: [email protected] <[email protected]> On Behalf Of Jason Weisberger via groups.io ? On Thu, Apr 3, 2025 at 01:04 PM, Charles Adams wrote:
? Can you please elaborate on preselector vs splitter?? I assume you're calling a splitter what I've been calling a preamp sure to the split output.? Is a preselector then a receive amp without the integrated split? |
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Capacitors in DB4332B and DB4333B
开云体育I am trying to determine the values of variable capacitors in DB Products Low Pass Filters to see if I can convert an 800 Mhz LPF that I bought in a flea market to a 450 Mhz LPF by just changing the inductors between the capacitors.Here is the setup. I bought two DB4333B type low pass filters for 850 Mhz for a very reasonable price.? The actual model number listed on the cases is 020252-004.? The frequency range is 851-869 Mhz.? There are N females on both input and output.? Coincidentally, there is not a model number in the Spectra catalog that shows N(F) to N(F).? The specific frequency range is also not listed in the catalog, but are wider. I assume this is some kind of OEM model number.? It is labeled Decibel. The inductors in the 800 Mhz LPF between the four capacitors are bare, straight, and no turns.? I would like to move the cutoff frequency to convert these to the same as a UHF DB4332B to use on an isolator for my amateur UHF repeater.?? I already have a couple of DB 4332B LPF's for UHF (450 -512 Mhz). The inductors look like 2 1/2 turns on the input and output and 3 1/2 turns between the two inner capacitors. I tried to measure the capacitors in both of these LPF's, but considering the capacitors are in the pf range, it was not that easy to deal with stray capacitances. Does anybody know the capacitor values in the the DB4333-2450 and DB 800 Mhz LPF's? If the capacitors between eh 450 and 800 Mhz are the same value or even close, I should be able to lower the LPF cut-off by increasing the number of turns in the filter to the same number as the DB4332-A. If the capacitors between 450 and 800 Mhz are different, I will just have to cut and try and see what shows up on the spectrum analyzer.? I did not want to solder and unsolder inductors to the expensive piston type trimmers and damage them with heat. The wire looks like #12 to me and is covered with shellac in the UHF and plain old copper wire for the 800 Mhz device?? I have measured the diameter of the coils in the 450 Mhz LPF and have it written down, someplace?? I am just trying to avoid buying additional DB4332B LPF's or equivalent replacement capacitors. That would turn my "reasonable price" into a "not so reasonable price."? Thanks. Micheal Salem N5MS |
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Re: F/S TPL PA6-1AE UHF amp
开云体育Sounds like a plan. I have a few other repeaters around that are GMRS or back ups. But if you want to continue this thread, you can email me on my QRZ email, WI9HF. Don't want to tie up the list.Chad Nelson WI9HF/WRPL979 Janesville Wisconsin 608-754-8671 Send from my spectrum iPhone 16. On Apr 3, 2025, at 7:15?PM, Kory Oldham W4RZ <Kory@...> wrote:
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Re: F/S TPL PA6-1AE UHF amp
开云体育I fully agree, you would basically just be changing out labels with the name on it. I am just keeping an eye out for a good deal for a spare for our system. I do not want to buy another brand new one just have it sit on the shelf LOL. Kory On 2025-04-03 20:05, Chad Nelson wrote:
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Re: F/S TPL PA6-1AE UHF amp
开云体育Yeah, I figured the TPLM would work good for my purposes here so I'm gonna hang onto that, but there really isn't any need to sell one to buy another one that's almost kind of silly.Chad Nelson WI9HF/WRPL979 Janesville Wisconsin 608-754-8671 Send from my spectrum iPhone 16. On Apr 3, 2025, at 6:54?PM, Kory Oldham W4RZ <Kory@...> wrote:
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Re: F/S TPL PA6-1AE UHF amp
开云体育Not sure what you budget is, I think you said UHF, have you looked at Bridgecom website? They have new Henry Radio Manufacture Amps. I'll link the UHF for easy lookup. Kory W4RZ On 2025-04-03 19:49, Chad Nelson wrote: Hi, I will hang onto that TPL amp at this point. I was trying to find |
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Re: F/S TPL PA6-1AE UHF amp
Hi, I will hang onto that TPL amp at this point. I was trying to find
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another amp, but I am trading apples for apples at this point. Will take advice and keep the TPL. Thanks for your interest. -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Kory Oldham W4RZ Sent: Thursday, April 3, 2025 5:35 PM To: [email protected] Subject: Re: [repeater-builder] F/S TPL PA6-1AE UHF amp Chad, Do you have any pictures of the amp? You can email me directly if you prefer. Kory W4RZ (good on QRZ) On 2025-04-03 15:05, Chad Nelson wrote: Hi all, I'm going to go in a different route with my amplifier so I |
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Re: Where did db Products go?
开云体育They did. ? ? From: [email protected] <[email protected]> On Behalf Of Tom Cole
Sent: Thursday, April 3, 2025 6:11 PM To: [email protected] Subject: Re: [repeater-builder] Where did db Products go? ? I think Comscope bought them.
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Re: F/S TPL PA6-1AE UHF amp
开云体育??????????????? You guys convinced me to keep the TPL, so it is going to be put in service with the TK851. ? Some things I have never tried before make me nervous to try, sounds like I have gotten good advice off this list. ? Thanks all. ? Chad ? From: [email protected] <[email protected]> On Behalf Of Jeremy Hansen via groups.io
Sent: Thursday, April 3, 2025 6:20 PM To: [email protected] Subject: Re: [repeater-builder] F/S TPL PA6-1AE UHF amp ? The PA6-1AE should be adjustable to and stable at 70w. I second that the TKR-851 will adequately provide a stable low drive output appropriate for your amplifier. You have everything you need. ? On Thu, Apr 3, 2025, 6:10?PM Mike via <prcradio=[email protected]> wrote:
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Re: F/S TPL PA6-1AE UHF amp
All Chad needs do is drop the TKR down to 1 watt and start
there...
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Ken At 04:19 PM 4/3/2025, you wrote: The PA6-1AE should be adjustable to and stable at 70w. I second that the TKR-851 will adequately provide a stable low drive output appropriate for your amplifier. |
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Re: UHF Repeater Input Frequency Issues
The only problem not terminating a divider is causing some amplitude ripple in the passband. It wont hurt the associated amplifier. If the preamp was working it could improve the system noise figure as its in front of any lossy components in the receiver, assuming its not getting blitzed due to no preselector.? |
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Re: UHF Repeater Input Frequency Issues
On Thu, Apr 3, 2025 at 01:04 PM, Charles Adams wrote:
Can you please elaborate on preselector vs splitter?? I assume you're calling a splitter what I've been calling a preamp sure to the split output.? Is a preselector then a receive amp without the integrated split?
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Re: F/S TPL PA6-1AE UHF amp
The PA6-1AE should be adjustable to and stable at 70w. I second that the TKR-851 will adequately provide a stable low drive output appropriate for your amplifier. You have everything you need. On Thu, Apr 3, 2025, 6:10?PM Mike via <prcradio=[email protected]> wrote:
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Re: UHF Repeater Input Frequency Issues
On Thu, Apr 3, 2025 at 01:10 PM, Ralph Mowery wrote:
We've figured out that the desensing was caused by the duplexer being out of alignment.
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This pictured preamp died in a storm last night causing further issues.? That being said, you're absolutely correct.? An 8 way split is 11dB of loss and that preamp is presumed to be 12dB gain.? I'm probably causing reflections back into the amp without termination of those ports, but the amp is likely doing little good anyway. If we grab another one in the future, it will be 1 port in, 1 port out.
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Great observation, and something I should have caught.
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Re: Where did db Products go?
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On Apr 3, 2025, at 6:09?PM, DCFluX via groups.io <dcflux@...> wrote:
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Ken Arck AH6LE
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