Re: Capacitors in DB4332B and DB4333B
Alex:
Thank you for these pictures. This is very helpful information. I
have a Johanson catalog and tried to match the capacitors at least
in physical size.? It did occur to me the capacitor values might
be 0.8 to 10 pf. because I think that is the same value used in
the DB4076 duplexers.? The capacitor in the 850 MHz LPF are the
physical same size, but that is all I can say. It looks like DB
broke off the little lug on the end since they soldered to the top
of the capacitors.
Your construction is very well done. The wire in the UHF LP is
insulated magnet wire and is 1 mil in width and I figured that was
18 AWG.? The wire in the 850 LPF is just bare wire, but also 18
AWG.
The coil in the UHF LP had been slightly pushed down in the UHF LP
case and it made me wonder if that was done to change the value or
to help the return loss.? But the wire looks a little long and
they pushed it down to get it away from the lid.? Your neat work
suggests that deformation? is not necessary.?
If the capacitors in the 850 LPF are not the same capacitor values
as the UHF, I did see some of the values you mentioned? on eBay.?
I have two of those 850 Mhz LPF's and one looked fine on the
spectrum analyzer, but the other did not. This makes me think some
of the capacitors in the one with the bad curve are broken.? So I
may be buying capacitors from the listing you suggested anyway. I
will know if the capacitors are the same when I put the coil in
the good LPF.
The only difference I had was that I tried to measure the coil
diameter and got it roughly at 1/4"instead of 7/32". I have some
18 AWG magnet wire here at my office and was going to wind it
using a drill bit as a form.??
Thank you Jeff for your suggestion of using a single piece of
wire. That sounds like a very good idea and I am going to try
that.? I was not going to disturb the connections from the input
to the first capacitor or the output to the last capacitor, but
may go ahead and wind it all as a single piece as you suggest.?
The coils for the 850 LPF are a single piece of wire zigzagged
across the four capacitors.
Thanks again.?
Micheal Salem N5MS
On 4/4/2025 11:28 AM, Alex wrote:
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About 3 years back I had one DB4332-B UHF low pass filer but needed two, so decided to reverse engineer it and build a clone. The variable piston capacitors are Johanson 0.8 - 10Pf rated at 150V. Back then I found several sellers on ebay offering them, and there was one selling them in 4 packs for $25 plus some shipping. The trimmer cap model I used was PC25J100. The model is stamped onto the top solder side of the cap, so usually not possible to see in the original LPF. Just checked on ebay but original listing is gone, however looks like listing #256220267439 is the same guy still offering those trimmer caps in packs of 4 still at the same price.
The 3 coils are made of #18 wire, one side being 2T, the middle one 3.5T and the last one again 2T. Coil diameter is 7/32 or about 5.55m, stretched out same as the original coils.
I also managed to find on ebay someone selling the identical metal boxes (Pomona model 2413) for $10-15 new old stock in the original bag and with connectors on each end, but these instead had one SO-239 and one PL259, which both where very easy to replace with NM/NF. I then also had to drill the four holes to mount the trimmer caps and assemble everything. The clone LPF was then checked on a VNA and compared to the original DB4332 and it had basically identical characteristics as the original one, and of course also tuned up just fine.
About a year later after that I needed two additional UHF LPFs and did build two additional clones that also worked perfectly. The attached picture shows the original LPF at the top, and one of my clones in the blue box at the bottom.
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Anyone have experience using a TDR to locate an underground fault for high voltage ?
There's a PUD in central Washing that can't appear to fix an outage for the past three weeks or so.
It's affecting several comm sites and one ski area. It's high up around 7,000 ASL with 20-foot drifts. ?The road is derivable around the first or second week of July each season.?
?
I'm not sure if it's incompetence or lack of training but the concept seems simple enough to me; send a pulse down the line and watch for the return indicating something is wrong.?
There are several of these units on the market, on line.?
?
I also suspect it's not an exact science and requires lots of experience to be effective.?
If I were in the area I suppose I could hook up the (dead) line to a spark plug circuit (from an engine or whatever) and walk the mile line listening for anomalies with an AM radio.?
For now, one leasee is dragging large amounts of propane to keep one site alive.?
--
-
Regards, Karl Shoemaker
To contact me, please visit SRG's web site at?
for the current email address.
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Re: Amphenol Old Style RG-393?
I think you guys figured it out. It is 0.43 outside diameter and looking up RG-225/U yields the same cable that I have. The cable I have has absolutely no markings on it. The only reason I know it was made by Amphenol is because there was a ribbon on the spool saying "Amphenol Electronics Corporation" on it. It has a single layer of outer woven braid from what I can tell.?
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Re: Suggestions for service monitor
I bought a Motorola R2600C for $600 and then about a week later picked up a Motorola R2550 with tracking generator for $400. I already have a Rigol DSA815TG spectrum analyzer that I use for filter tuning.
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Re: Varden duplexer model# 8D1146B
Could you upload some photos of it?
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Re: Possibly Quintron PA? Need help identifying transistors
Ken, You are likely right but if I had the part number off the board I could confirm. There were some 100 watt mid band boards as well. The coils look different from the UHF ones I have here.?
Ken Pearce? N4KCD? Commerce Township, MI
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On Apr 7, 2025, at 21:49, Ken Arck AH6LE via groups.io <ken@...> wrote:
?
Quintron QT-6700 (UHF) was 90 watts.I have a spare here and his board
looks nothing like the one I have
Ken
At 06:34 PM 4/7/2025, you wrote:
Just looking at it, especially
the LP filter, I'd say UHF...lots of strip line used
Chris WB5ITT
On Mon, Apr 7, 2025, 8:29 PM Tyler- WZ5TX via
<wz5tx=[email protected]
> wrote:
- I have this PA and it is labeled ?�?100W PA?�?.
- However I cannot find the datasheet for the transistors. Motorola
SRF2604.
- any ideas what the range for this is?
- drive needed?
-
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President and CTO - Arcom Controllers
Makers of repeater controllers and accessories
Phone: (503) 678 6182
Authorized Dealers for Kenwood and Telewave.
We offer complete turn-key repeater packages!
"We don't just make 'em. We use 'em!"
![[]](http://www.arcomcontrollers.com/arcom.png)
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Re: Possibly Quintron PA? Need help identifying transistors
Quintron QT-6700 (UHF) was 90 watts.I have a spare here and his board
looks nothing like the one I have
Ken
At 06:34 PM 4/7/2025, you wrote:
Just looking at it, especially
the LP filter, I'd say UHF...lots of strip line used
Chris WB5ITT
On Mon, Apr 7, 2025, 8:29 PM Tyler- WZ5TX via
<wz5tx=[email protected]
> wrote:
- I have this PA and it is labeled ?�?100W PA?�?.
- However I cannot find the datasheet for the transistors. Motorola
SRF2604.
- any ideas what the range for this is?
- drive needed?
-
![[]](/g/repeater-builder/attachment/214406/)
Content-Type: image/jpeg; name="photo-3.jpg"
Content-Disposition: inline; filename="photo-3.jpg"
Content-ID: <[email protected]>
X-Attachment-Id: [email protected]
------------------------------------------------------------------------------
President and CTO - Arcom Controllers
Makers of repeater controllers and accessories
Phone: (503) 678 6182
Authorized Dealers for Kenwood and Telewave.
We offer complete turn-key repeater packages!
"We don't just make 'em. We use 'em!"
|
Re: Possibly Quintron PA? Need help identifying transistors
Need the part number on the other side. Post a pic of the other side. Looks like a Possible mid band board.?
Ken Pearce? N4KCD? Commerce Township, MI
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On Apr 7, 2025, at 21:34, Chris Boone WB5ITT via groups.io <setxtelecom@...> wrote:
? Just looking at it, especially the LP filter, I'd say UHF...lots of strip line used
Chris WB5ITT
I have this PA and it is labeled “100W PA”.
However I cannot find the datasheet for the transistors. Motorola SRF2604.
any ideas what the range for this is?
drive needed?
|
Re: Possibly Quintron PA? Need help identifying transistors
Just looking at it, especially the LP filter, I'd say UHF...lots of strip line used
Chris WB5ITT
I have this PA and it is labeled “100W PA”.
However I cannot find the datasheet for the transistors. Motorola SRF2604.
any ideas what the range for this is?
drive needed?
|
Possibly Quintron PA? Need help identifying transistors
I have this PA and it is labeled “100W PA”.
However I cannot find the datasheet for the transistors. Motorola SRF2604.
any ideas what the range for this is?
drive needed?
|
Re: Amphenol Old Style RG-393?
Looked it up in a Nemal Electronics Catalog, and you remembered correctly, Jeff. Both cables are identical except for the jacket on RG393 is -70 to +200 degree C fluorinated ethylene propylene (FEP) and OD 390 mils. RG225 is -70 to +250 degrees C and fiberglass/ silicone braid and OD 430 mils Both should say Mil C-17D, just a little higher operating temp on RG225.
John
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On 04/07/2025 6:04 PM EDT Jeff DePolo WN3A via groups.io <jd0@...> wrote:
? It is an older variant of RG-393. I know it's 393 and I know it's 50 ohms.
Apparently, I didn’t receive the original post, only your follow-up response. Questions:
1. What is the measured OD of the cable?
2. Does it have a single layer of woven braid for the jacket or two layers?
3. Does it feel like fiberglass or something else like a high-temp polymer?
4. It is actually marked Amphenol and RG-393? Any other markings, part number, etc.?
I’ve seen/used this type of cable in high-temperature and high-power applications; I even have a few jumpers here. What confuses me is that I remember it being larger in diameter than RG-393 (390 mils), and likewise, what I have here at the shop is also larger OD - 430 mils or thereabouts, close to RG-214 if not a hair bigger. What I have here has no markings on it all, but I've always known this type of cable to be RG-225.
Also, I don’t remember ever seeing any marked as RG-393, so that’s why I asked about what is printed on your cable. I do have some old Amphenol catalogs around somewhere, but in the meantime, look up RG-225 to see if that’s close to what you have.
--- Jeff WN3A
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Hi Greg,
?
Several things from the school of hard knocks...? Recheck the length of your VB-35 matching section with at least several feet of 50 ohm coax between it and your measuring instrument as I found it was different if directly connected to a tower mounted diplexer N female input, than if a length of 50 ohm coax in the middle. I do not have a DB cutting chart, but have a few more DB lengths. DB said for 53.23 MHz, the length of VB35 should be 36 5/8 inches. I have a note that for 52.8 MHz the distance from open end of the N female to the UHF barrel tightening ring should be 37" so that includes the UHF barrel. So you must be close and as you said tuning is broad.
?
If you are using the end supports to the tower leg placed out 2/3 on the element ,for 53.1 MHz 1.02SWR, top to metal center support top is 49 3/8", bottom tip to metal center support bottom is 50 3/8" (our test set-up on a tower leg free and clear)
?
We found the factory? N connectors pulled apart with tower icing and high winds, so I went to 2 piece N connectors, but if you used thick wall heat shrink like used for underground? electrical wiring, on your T and N connector, you should be OK.
?
John
On 04/07/2025 5:55 PM EDT wgwl via groups.io <wgwl@...> wrote:
?
?
Roger,
In hopes of answering your original question, I got my hands on a DB212-2 originally on 37.7MHz and shortened the antennas and matching section for 6?
meters. The 35 ohm matching section (Decibel Products VB-83 cable) was shortened?
to 36.25" end to end. With a UHF T on the end?
and two 50 ohm loads attached resulted in the attached plot. As you can see, the?
exact length is not critical across the band.
?
John,
You mentioned "DB factory lengths" in an earlier post. Do you have access to the?
actual factory length chart for 6M ? If so, please share.
?
Mike,
How well did the tuning of your antenna on the ground translate to mounting on a tower? What length of pipe did you use when tuning?
Greg
WB9TRO
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Re: MTR2000 channel steering
Such as? The RSS is pretty easy to navigate?
Chris WB5ITT?
Thanks for your input, however I'm looking for help programming the MTR2000 instead of a functional description.
73
-de John NI0K
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Re: Suggestions for service monitor
I second this. I had the same question about a month ago and ended up getting an HP8921A. It’s a good analyzer to learn on and does probably way more than you need.?
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On Apr 7, 2025, at 6:42?PM, Mike via groups.io <prcradio@...> wrote:
? For non digital stuff the HP/Agilent 8920 series.?
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Re: Suggestions for service monitor
For non digital stuff the HP/Agilent 8920 series.?
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Re: Suggestions for service monitor
The NanoVNA-V2 seems to handle doing the pass part pretty well. You're measuring return loss there, and it seems to handle that just fine. Only question I might se is if the frequency standard is really accurate enough to set it correctly-but I bet it's pretty close...
Notches on the other hand-forget it. Definitely not even close to enough range for that. Even most service monitors can't do it, or are right on the edge of doing tolerably.
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On 4/6/2025 5:34 PM, Bob Dengler via groups.io wrote: At 4/6/2025 01:35 PM, you wrote:
Ooh this is interesting. I have a NanoVNA and I think I asked here and also saw some other threads here that were saying its dynamic range is not enough to tune a duplexer. LibreVNA looks a lot more capable! I've seen reports of drift issues with the LibraVNA.? For the moment I'm happy with my VNWA 3EC (though the design is getting dated so not sure I'd recommend for a new purchase), but if I needed one today I'd try this one: < <>>
Bob NO6B
_._,_._,_
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Re: Amphenol Old Style RG-393?
? It is an older variant of RG-393. I know it's 393 and I know it's 50 ohms.
Apparently, I didn’t receive the original post, only your follow-up response. Questions:
1. What is the measured OD of the cable?
2. Does it have a single layer of woven braid for the jacket or two layers?
3. Does it feel like fiberglass or something else like a high-temp polymer?
4. It is actually marked Amphenol and RG-393? Any other markings, part number, etc.?
I’ve seen/used this type of cable in high-temperature and high-power applications; I even have a few jumpers here. What confuses me is that I remember it being larger in diameter than RG-393 (390 mils), and likewise, what I have here at the shop is also larger OD - 430 mils or thereabouts, close to RG-214 if not a hair bigger. What I have here has no markings on it all, but I've always known this type of cable to be RG-225.
Also, I don’t remember ever seeing any marked as RG-393, so that’s why I asked about what is printed on your cable. I do have some old Amphenol catalogs around somewhere, but in the meantime, look up RG-225 to see if that’s close to what you have.
--- Jeff WN3A
|
Roger,
In hopes of answering your original question, I got my hands on a DB212-2 originally on 37.7MHz and shortened the antennas and matching section for 6?
meters. The 35 ohm matching section (Decibel Products VB-83 cable) was shortened?
to 36.25" end to end. With a UHF T on the end?
and two 50 ohm loads attached resulted in the attached plot. As you can see, the?
exact length is not critical across the band.
?
John,
You mentioned "DB factory lengths" in an earlier post. Do you have access to the?
actual factory length chart for 6M ? If so, please share.
?
Mike,
How well did the tuning of your antenna on the ground translate to mounting on a tower? What length of pipe did you use when tuning?
Greg
WB9TRO
|
Re: Amphenol Old Style RG-393?
I don't think you understood my question...I am asking about this specific cable. It is an older variant of RG-393. I know it's 393 and I know it's 50 ohms. I'm aware of every RF connector. I'm looking for information on this specific style of 393. The internet is of no help on this cable. Termination is definitely different than the solid FEP because of the braided sheath. Obviously need to keep it from unraveling itself.?
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Varden duplexer model# 8D1146B
Hello all, would anyone have any tuning information on the Varden duplexer 146-148mhz. I know its a long shot, but no searches on the web produced any results.?
?
These were made by
Varden Electronics
Box 791, Jackson, Michigan
49204
?
Thanks for any information
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Karl Shoemaker
Jared Smudde
Ken Arck AH6LE
Chris Boone WB5ITT
Tom VA3TS