I was really disappointed in the looks of my old #47 bulbs in my 4A line so I changed the bulbs out for LEDs finally.
Not only do they keep the front of the radio so much cooler, the looks are so much improved.
I bought the wrong LEDs, they were cool white and not frosted.? A few minutes with some sandpaper and a yellow
Sharpie fixed them up though.
My iPhone didn't capture the look very well, they look even better in person.? All the original Lagoon Blue filters
are still fine.
73,
Gary
WB6OGD
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Re: R4B 50 Khz I.F. sweep.
Hi Dave!
I use an Elecraft K3 with a P3 daily, and when I refurbished my old(ish) B-twins a few years ago I wanted to see the effect of the variable passband filtering, so that meant looking at the 50 kHz IF.? I used a small impedance buffer preamp mounted under the chassis of the R-4B near the 50 kHz amp V5 feeding an SMA in the 'Spare' jack position on the rear skirt and feed an .? It was the only one I could find which went below 100 kHz, indeed it will receive as low as 500 Hz.
Of course there are issues: the 50 kHz LO feeds through to V5 and shows up as a constant peak in the display, but that is a minor complaint.? In general it works well, but those of us spoiled by steep crystal filters and DSP IFs, or in my case the will find the resulting passband shape factor to be somewhat...lumpy may be a good word?? I have been a broadcast engineer for 40 years and have serviced more FM transmitters (I love my old Gates FM-1H!), receivers and ham gear than I care to remember so although I will not claim to be the most expert RF aligner, I do have a passing familiarity with RF and IF alignment.? This being said, I ran through a full alignment as per the manual and the receiver works gangbusters.? Sensitivity is on par with my K3 but sounds SOOOO much better and the analog passband tuner is a thing of beauty compared to the DSP filtering in the K3 which gets harsher the more narrow you squeeze it.? Despite this fine performance, the 50 kHz IF passband shape is still not as nice as a crystal filter...I'll bet NC0B would see much better results on his modded R-4C, still it is nice to be able to see the band activity on my PC, it is usable and fun to see.
Cheers & 73,
Howie / WA4PSC
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Re: R4B 50 Khz I.F. sweep.
Boy that was a fast response thanks guys for the tips. The SA I have is a Rigol 815TG? which is the same unit WA8SAJ uses so figured I was good to go unfortunately I'm a little new to spectrum analyzers' operation. The first test I did was the 5645 Khz sweep with the SA connected through a blocking cap to pin1-V2 then used a small coil of insulated wire to basically sniff on the underside of V3. There was enough signal to draw a pattern on the SA seemed to work really well. Think I will revisit the 5645 test again without a direct connection to see if there's any difference in SA response.?
?In regards to the 50Khz test, I was directly connecting the TG through a blocking cap in multiple places without success, and from what you all said this is the wrong test setup to use. Was also using a blocking cap for the SA input as well I will refine my connections and report back as long as I can find the right test points for TG and SA input.
Dave
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Re: R4B 50 Khz I.F. sweep.
For my single conversion Hammarlund alignments I make extensive use of an SA - the Hammarlund folks at the factory were funny about that. Anyway, any of the new generation SA's like Siglent, Rigol, etc., will sweep +/- 50 kHz.
For the HQ's I loosely couple in around the insulated wire feeding the mixer and sample out by connecting around an insulated wire feeding the detector. No direct probe to tube pin connections. Safe and minimal to no loading of the circuit.
Don't have an R-4B nor a schematic but, in general, I'd repeat my Hammarlund connection scheme and suggest injecting 50 kHz at the 2nd mixer and tapping off the return signal at the diode detectors? Should work.
Loose coupling as Rob suggests is the goal, like clamping around an insulated wire.
I'd never make a direct metal to probe connection with a sensitive SA, or at least not without a very good reason and first thoroughly characterizing the connection point with a multimeter.
Dan
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On Mar 19, 2023, at 8:39 PM, Rob Sherwood <rob@...> wrote:
?
When I sweep something like this I feed in the tracking generator signal, preferably a stage before, through with around a 10k resistor. ?The I preferably use an FET probe to pick off the signal that goes back into the spectrum analyzer. ?A 10X passive probe
may work but the termination will be wrong. ?
You likely won¡¯t be able to measure the ultimate rejection of the filter, but you can see the passband shape you are possibly tweaking. ?
Rob, NC0B
On Mar 19, 2023, at 6:25 PM, W6MQI via groups.io <w6mqi@...> wrote:
?Guess I should mention I have the exact same spectrum analyzer as WA8SAJ used in his test.
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Re: R4B 50 Khz I.F. sweep.
I have a 3585B. A beautiful instrument. I also have a 8594E with TG and narrowband options that is a bit more portable. It's spec-ed down to 9 KHz but I've never pushed it that low. My NanoVNA claims coverage to 50KHz. Might work OK on a Drake low IF. 73 -Jim NU0C On Mon, 20 Mar 2023 00:39:54 +0000 "Rob Sherwood" <rob@...> wrote: I use an HP 3585A which is good from audio through 40 MHz. Rob, NC0B
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Re: R4B 50 Khz I.F. sweep.
I use an HP 3585A which is good from audio through 40 MHz. Rob, NC0B
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On Mar 19, 2023, at 6:31 PM, Jim Shorney <jimNU0C@...> wrote:
?
50 KHz is hard. Most analyzers that could fall into ham hands don't go down that far. I have an old HP that goes down to 20 Hz but it would anchor a decent size boat.
73
-Jim
NU0C
On Sun, 19 Mar 2023 17:17:32 -0700
"W6MQI via groups.io" <w6mqi@...> wrote:
Has anyone ever tried to sweep the 50Khz I.F. in the R4B with a spectrum analyzer? WA8SAJ had a powerpoint presentation a few years ago showing screenshots using his SA to sweep the 50 Khz I.F., but he gave no real explanation of how he performed the test and adjustments for the passband curves. I have tried to reproduce his SA sweeps without success just can't seem to find the right input for the tracking generator and output from the R4B to the SA input. Anyone have success performing this procedure?
Dave
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Re: R4B 50 Khz I.F. sweep.
When I sweep something like this I feed in the tracking generator signal, preferably a stage before, through with around a 10k resistor. ?The I preferably use an FET probe to pick off the signal that goes back into the spectrum analyzer. ?A 10X passive probe
may work but the termination will be wrong. ?
You likely won¡¯t be able to measure the ultimate rejection of the filter, but you can see the passband shape you are possibly tweaking. ?
toggle quoted message
Show quoted text
On Mar 19, 2023, at 6:25 PM, W6MQI via groups.io <w6mqi@...> wrote:
?Guess I should mention I have the exact same spectrum analyzer as WA8SAJ used in his test.
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Re: R4B 50 Khz I.F. sweep.
50 KHz is hard. Most analyzers that could fall into ham hands don't go down that far. I have an old HP that goes down to 20 Hz but it would anchor a decent size boat. 73 -Jim NU0C On Sun, 19 Mar 2023 17:17:32 -0700 "W6MQI via groups.io" <w6mqi@...> wrote: Has anyone ever tried to sweep the 50Khz I.F. in the R4B with a spectrum analyzer?? WA8SAJ had a powerpoint presentation a few years ago showing screenshots using his SA to sweep the 50 Khz I.F., but he gave no real explanation of how he performed the test and adjustments for the passband curves. I have tried to reproduce his SA sweeps without success just can't seem to find the right input for the tracking generator and output from the R4B to the SA? input.? Anyone have success performing this procedure?
Dave
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Re: R4B 50 Khz I.F. sweep.
Guess I should mention I have the exact same spectrum analyzer as WA8SAJ used in his test.
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?
Has anyone ever tried to sweep the 50Khz I.F. in the R4B with a spectrum analyzer?? WA8SAJ had a powerpoint presentation a few years ago showing screenshots using his SA to sweep the 50 Khz I.F., but he gave no real explanation of how he performed the test and adjustments for the passband curves. I have tried to reproduce his SA sweeps without success just can't seem to find the right input for the tracking generator and output from the R4B to the SA? input.? Anyone have success performing this procedure?
Dave
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I think this is an example of the "real hams" make their own cables claim many like to make, he's just making an allowance for the elderly and handicapped... Ken, N2VIP
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On Mar 19, 2023, at 17:36, Jim W7RY via groups.io <jimw7ry@...> wrote:
?
At what age does elderly start??
Are you sure they wont sell them to the young or non handicapped?
Just askin...
Jim W7RY
On 3/19/2023 5:26 PM, Gregory Beat via
groups.io wrote:
Elderly or handicapped radio amateur can buy pre-made cables for
Drake?4-line Twins or Collins S-line?
from Joel at RF Connection (Gaithersburg,
MD)
RG-58 or RG-62 coax cable (you request).
<424FE80E-0C4C-4199-BD55-78BA72409F81.jpeg>
--
Thanks and 73, Jim W7RY
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At what age does elderly start??
Are you sure they wont sell them to the young or non handicapped?
Just askin...
Jim W7RY
On 3/19/2023 5:26 PM, Gregory Beat via
groups.io wrote:
Elderly or handicapped radio amateur can buy pre-made cables for
Drake?4-line Twins or Collins S-line?
from Joel at RF Connection (Gaithersburg,
MD)
RG-58 or RG-62 coax cable (you request).
--
Thanks and 73, Jim W7RY
|
Elderly or handicapped radio amateur can buy pre-made cables for Drake?4-line Twins or Collins S-line? from Joel at RF Connection ( Gaithersburg, MD)RG-58 or RG-62 coax cable (you request). 
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DRAKE TECHNICAL NET UPDATE ( March 19, 2023 )
Today we had 31 stations checking into the net on 7.238. It was a bit rough with the Virginia QSO part?going on, but we made it through with little difficulty.?
The following radio's were used to check in.?
Twins = 10 TR4(x) = 5 TR5 = 1 TR7(x) = 5
73's, Mark, WB0IQK
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Re: Success- the vernier drive on my T-4XC is back together and working.
I tend to leave the drive alone unless there¡¯s a problem with moving the slug rack. The problem usually manifests itself at the high frequency end (10m). If resetting the preload won¡¯t fix it, then I¡¯ll take it out, clean it, inspect it and try to reposition the shaft as needed after putting in new grease.?
Even when I wash the chassis, I won¡¯t take apart a working drive. I keep the detergent away from the drive.?
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent from Proton Mail for iOS
On Fri, Mar 17, 2023 at 21:36, Bill Leonard N0CU < billincolo73@...> wrote: After trying unsuccessfully for several days to reassemble the vernier drive on my T-4XC, I noticed a small ball bearing on the carpet under my work bench. Since the vernier drive is the only thing I had been working on that had any bearings, I assumed that it must have fallen out of the drive while I was removing it from the T-4XC. It turns out that this bearing is used as a spacer inside the large shaft. After placing it next to the spring inside the large shaft, I was able to reassemble the drive with just a slight amount of preload. The preload required is only that required to get the set screws on the large shaft to fit into the notch on the main shaft. The main shaft is the one that moves the coil slugs. The preload needed can easily be generated by a medium size screwdriver and no special clamp is required. Although removing the vernier allowed me to remove all of the old grease, I am not sure the improvement over what was achieved by simply cleaning the drive in place justifies the extra work involved in reassembling the drive.
--
Bill N0CU
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Success- the vernier drive on my T-4XC is back together and working.
After trying unsuccessfully for several days to reassemble the vernier drive on my T-4XC, I noticed a small ball bearing on the carpet under my work bench. Since the vernier drive is the only thing I had been working on that had any bearings, I assumed that it must have fallen out of the drive while I was removing it from the T-4XC. It turns out that this bearing is used as a spacer inside the large shaft. After placing it next to the spring inside the large shaft, I was able to reassemble the drive with just a slight amount of preload. The preload required is only that required to get the set screws on the large shaft to fit into the notch on the main shaft. The main shaft is the one that moves the coil slugs. The preload needed can easily be generated by a medium size screwdriver and no special clamp is required. Although removing the vernier allowed me to remove all of the old grease, I am not sure the improvement over what was achieved by simply cleaning the drive in place justifies the extra work involved in reassembling the drive.
-- Bill N0CU
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For what it's worth, Drake does call it AGC on the schematic.? His statement as I read it is saying that as shipped with the 1 Meg AGC does not work properly and adding the 15K makes it work, At least that's the way I read it. It is also stated this was fixed in later T4's.
I saw this statement in another search -
The 15k AGC resistor is wired across the 1meg AGC resistor that was installed by the factory.? At least that is what Drake did in my T4X.? The 1meg was a design mistake by Drake that was fixed in later models.? A quick solution to the problem was to simply wire a 15k across the 1meg and settle for slightly less than 15k.? With a 1meg resistor there was no AGC.
Regards,
Frank Kamp, K5DKZ,? July 14, 2002
I wonder if K5DKZ is a member of this group? Perhaps he can explain it.
?
Doug, WA3DSP
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I have read that years ago, noted it on my schematic.
I do find it hard to believe a Drake factory screw up that makes it to not work!
I do have my T-4X on the bench right now, I will try to check it out.
I remember back in the day guys were bending a tube pin out to disconnect all ALC..? made for a bigger signal but with splatter.
They were hams but thought like CBer's.? Lowering that resistor might do pretty much the same.
Yes, AGC is ALC..? I am pretty sure Drake called it ALC, he is the only one calling it AGC, though it is the same.
Gain vs. Level.. pretty much the same to me, hi hi.
73,
Gary
WB6OGD
?
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In this article on conversion to 6146's? -? He states the following. This seems like a radical change of value. Is this valid? Exactly what does AGC do? Is this really better termed ALC?
Connect a 15k ohm, half watt resistor from the plate of V1B (AGC amp) to ground. This may only be needed on the T4X to correct a factory screw-up. The original value of the resistor here was 1 meg which would ensure that there was no AGC action. No one really noticed so it may not be a big deal. If you want the AGC to work on an old T4X, install the 15k resistor. No need to remove the original 1 meg resistor, just wire the 15k across it.
Doug, WA3DSP
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Re: TR7 Service Kit - Extender Boards Needed
Yes, finding .156 connectors is easy, perhaps I should've asked ones that are compatible with the originals as far as pin dia is concerned along with the hooks that hook over the edge of the pcb so the connector is not distorted when plugged in and unplugged.... Thanks for your help.
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Gary WB6OGD
W6MQI
Jim Shorney
Rob Sherwood
Greg W9GB
Doug Crompton WA3DSP