Re: Drake W4 wattmeter part three
On 2024-01-21 09:21, mike bryce wrote: I¡¯m wondering if at one time someone swapped out the meter for
something much more sensitive instead of the stated 200uA one Drake
used. *** I can easily imagine somebody scoring a nice meter and just sticking it in. Once upon a time... ...As a preteen in San Francisco, I attended an after school electronics program known as "Lux Labs". We had lectures, and we built projects. One of our first projects was a crystal radio. The program provided us with all the parts, including a cheap headset. Down on Radio Row, I scored a really nice Western Electric headset. For some reason, my crystal radio never worked. The instructor checked all my wiring, pulled on my solder joints - all OK. But not a peep out of it. Some twenty years later, I woke up one morning, sat up in bed, and said "600 ohms!" ...which was surely the input impedance of that nice WE headset. Way too low for a crystal radio. - Jerry, KF6VB
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Re: W4 has 1N34A available for it.
I was going to buy some Fluke test meter leads from Amazon. After reading the reviews, it was apparent the leads Amazon was selling were fake Chinese junk.
mike wb8vge
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On Jan 21, 2024, at 12:19 PM, Lyndon VE7TFX <lyndon@...> wrote:
Frank Barnes writes:
Amazon will sell us all the 1N34A's we want and the prices are inexpensive,
about 60 cents each with free delivery for Prime members. And the odds are close to 100% that none of those are actual 1N34s.
Amazon semiconductors are almost guaranteed to be fakes. Don't Do
It.
--lyndon
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Re: Drake W4 wattmeter part three
Gang,
Before I celebrate too much, I have a couple more W4 meters that have the opposite problem¡ªtoo much deflection¡ªcan¡¯t set the calibration
If I apply 100W, the meter begs, and if you switch scales to 2000W, 100W of RF shows 900W
Again, a look at the simple schematic will help when I try to explain what I ended up doing.
On the 200W scale, trimmer R4 sets the calibration. On the 2000W scale, trimmer R4 is still used, but then R3, R2 are in series.
So I measured resistance between the cathode of D1 to the brown wire that goes to the 200W selector. I read 12K (the trimmer is actually 12K) and of course I can adjust the value down to about 100¦¸ or so.
Switch to 2000W scale, and measured about 80K¦¸ of resistance from the cathode of D1 to the wire that goes to the 2000W selector tab.
The wiring to both the 200W and 2000W meter positions are in perfect working order. So why does the meter go off scale no matter where the trimmers are set?
What I ended up doing was to insert a resistor in series with the wire that runs to the selector switch on both power levels.
On the 200W scale, I ended up with 62K, and the 2000W scale required a whopping 220K!
I¡¯m wondering if at one time someone swapped out the meter for something much more sensitive instead of the stated 200uA one Drake used.
Mike wb8vge
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Re: Drake W4 wattmeter woes and some success
On 2024-01-21 08:58, Ralph Mowery via groups.io wrote: Part of my job was to calibrate all kinds of instruments in a large
plant. *** I did that too! I worked in the instrument shop at GTE Lenkurt. Mostly I did repairs, but calibration was never far from our minds. We piped 10Mhz all over the plant to feed the various instruments. There was a rubidium standard in the back room. Once a day, a guy would set the old standard to the rubidium one using a Lissajous figure. - Jerry, KF6VB
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Re: W4 has 1N34A available for it.
Frank Barnes writes: Amazon will sell us all the 1N34A's we want and the prices are inexpensive,
about 60 cents each with free delivery for Prime members. And the odds are close to 100% that none of those are actual 1N34s. Amazon semiconductors are almost guaranteed to be fakes. Don't Do It. --lyndon
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Re: W4 has 1N34A available for it.
I purchased 1N34As on eBay and didn¡¯t figure they were actually silicon diodes until after the boards were stuffed and flow soldered.
Rob, NC0B
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On Jan 21, 2024, at 10:12 AM, jerry-KF6VB <jerry@...> wrote:
?On 2024-01-21 08:53, mike bryce wrote:
One has to be very careful about buying electronic parts from Amazon.
Lots of counterfeit stuff here. *** Reviews on one of the 1N34 listings say that they are silicon
Hot Carrier Diodes.
One can find 1N34A's that are believably authentic on Ebay.
- Jerry
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Re: W4 has 1N34A available for it.
On 2024-01-21 09:09, Paul Christensen wrote: Passives mostly seem OK, but I only purchase semiconductors through
industrial suppliers where there¡¯s accountability in the chain of
custody between time of manufacture and point of sale. *** I bought a baggie of cheap IRF510's from a discount house. When I wired them into an amp, they wouldn't take the quiescent. When I approached it - turning up the bias - they would just run away and burn up. Real 510s from Mouser worked fine. - Jerry, KF6VB
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Re: W4 has 1N34A available for it.
On 2024-01-21 08:53, mike bryce wrote: One has to be very careful about buying electronic parts from Amazon.
Lots of counterfeit stuff here. *** Reviews on one of the 1N34 listings say that they are silicon Hot Carrier Diodes. One can find 1N34A's that are believably authentic on Ebay. - Jerry
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Re: W4 has 1N34A available for it.
>¡±One has to be very careful about buying electronic parts from Amazon.¡± ? Passives mostly seem OK, but I only purchase semiconductors through industrial suppliers where there¡¯s accountability in the chain of custody between time of manufacture and point of sale.? I recently needed some MRF237 RF transistors ¨C a device long obsolete.? But miraculously, all the Motorola branded MRF237s ended up in China. ?For all we know it¡¯s a re-labeled 2N3053.? Same goes for Tayda Electronics that seemingly everyone loves.? Possibly their 741 op-amps and 1N400x diodes are OK, but I won¡¯t take the chance. ?? ? Paul, W9AC
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Re: Drake W4 wattmeter woes and some success
Thanks for? telling up the repair.
People put too much into the wattmeter numbers.? I just think that if any of the broad range wattmeters are with in about 10% that is good enough.? If I am thinking right just 1 db is about 25 % and that is hardly noticeable? on the receiving end.? I have several wattmeters and the? Drakes mostly match a Struthers I have.? I have 3 Heathkits and I just used the Struthers and set them to match it at 14 MHz and let it go at that.
When measuring the power of a transmitter I just note if it is within 10 % of what it is rated for.? If there is any? big change the next time I check it with the? same meter then I may start look for what the problem is, meter, dummy load , or transmitter.
Part of my job was to calibrate all kinds of instruments in a large plant.? We had two calibrators for each type of instrument? we calibrated and set everything to those calibrators? which were sent out every year for calibration.
Ralph ku4pt
On Sunday, January 21, 2024 at 11:37:58 AM EST, mike bryce <prosolar@...> wrote:
³Ò²¹²Ô²µ¡ An update on the W4 wattmeter. The one with the low readings and the inability to set the meter calibration has been fixed! The problem? Capacitor C5 showed about 3k¦¸ of resistance! Replaced C5 and C4 (why not?) and I could calibrated the meter. Now¡ according to Drake they want you to use 14mhz and apply so many volts RMS across the 50¦¸ dummy load with one value at 100W and the second at 1000W. I can¡¯t generated 1000W on 14mhz, so I set the 200W scale to 100 W, then set the 2000W scale to 100W. I know an analog? meter is not as accurate on the lower end of its scale, but that¡¯s the best I can do. Mike, wb8vge
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Re: W4 has 1N34A available for it.
One has to be very careful about buying electronic parts from Amazon.?
Lots of counterfeit stuff here.
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On Jan 21, 2024, at 10:50 AM, Frank Barnes < fbw4npn@...> wrote:
Amazon will sell us all the 1N34A's we want and the prices are inexpensive, about 60 cents each with free delivery for Prime members.
-- Frank Barnes
W4NPN
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
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Re: Drake W4 wattmeter woes and some success
³Ò²¹²Ô²µ¡
An update on the W4 wattmeter.
The one with the low readings and the inability to set the meter calibration has been fixed!
The problem?
Capacitor C5 showed about 3k¦¸ of resistance!
Replaced C5 and C4 (why not?) and I could calibrated the meter.
Now¡ according to Drake they want you to use 14mhz and apply so many volts RMS across the 50¦¸ dummy load with one value at 100W and the second at 1000W. I can¡¯t generated 1000W on 14mhz, so I set the 200W scale to 100 W, then set the 2000W scale to 100W.
I know an analog meter is not as accurate on the lower end of its scale, but that¡¯s the best I can do.
Mike, wb8vge
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Re: Drake W4 wattmeter woes...
Sounds like a plan¡ many thanks.
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On Jan 21, 2024, at 12:11 AM, K6OXN Bob < bobk6oxn@...> wrote:
Mike, I did find some of my 1N34A diodes that I used in my W4. I will place a couple in the mail to you to try. Don't have enough to fix 4 W4's but it might be a start.
73? Bob
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Re: W4 has 1N34A available for it.
Amazon will sell us all the 1N34A's we want and the prices are inexpensive, about 60 cents each with free delivery for Prime members.
[Edited Message Follows]
Germanium Diodes are used for Rectification/Detection (RF¡ª> DC)
in RF/SWR meters (and Antenna Tuners with Internal meters) due to low voltage drop (0.3V).
Common Germanium Diodes are: 1N34(A), 1N60, 1N270, and 1N295.
These Germanium Diodes DIFFER in their Voltage and Current Ratings.
DRAKE frequently used the 1N270 diode in many of their Antenna Tuners, Wattmeters.
==
Schottky Diodes (1N5819,?BAT41, BAT43), can be Substituted for Germanium diodes?
due to similar Low Voltage Drop (0.3-0.5V).? Silicon not suitable (0.7 V drop).
** At the millennium, with RoHS mfg. conversion, many types of Germanium diodes disappeared. **
Through-hole reduction, due to Surface Mount replacement, also a production issue.
¡ª
Central Semiconductor CDSH270 was a Schottky Diode designed to replace the 1N270 Germanium diode.
100V, 100mA, through-hole, DO-35 package Schottky diode.
Central Semi Discontinued, after a ~15 year production run.
Some advantages over the 1N270 are lower forward voltage, lower leakage current,
faster switching speed, and a more robust package.
greg, w9gb
-- Frank Barnes
W4NPN
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
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Re: W4 has 1N34A available for it.
Germanium Diodes are used for Rectification/Detection (RF¡ª> DC) in RF/SWR meters (and Antenna Tuners with Internal meters) due to low voltage drop (0.3V). Common Germanium Diodes are: 1N34(A), 1N60, 1N270, and 1N295. These Germanium Diodes DIFFER in their Voltage and Current Ratings. DRAKE frequently used the 1N270 diode in many of their Antenna Tuners, Wattmeters. == Schottky Diodes ( 1N5819,?BAT41, BAT43), can be Substituted for Germanium diodes? due to similar Low Voltage Drop (0.3-0.5V). ?Silicon not suitable (0.7 V drop). ** At the millennium, with RoHS mfg. conversion, many types of Germanium diodes disappeared. ** Through-hole reduction, due to Surface Mount replacement, also a production issue. ¡ª Central Semiconductor CDSH270 was a Schottky Diode designed to replace the 1N270 Germanium diode. 100V, 100mA, through-hole, DO-35 package Schottky diode.
Central Semi Discontinued, after a ~15 year production run.
Some advantages over the 1N270 are lower forward voltage, lower leakage current,
faster switching speed, and a more robust package.
greg, w9gb
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Re: Drake W4 wattmeter woes...
Mike, I did find some of my 1N34A diodes that I used in my W4. I will place a couple in the mail to you to try. Don't have enough to fix 4 W4's but it might be a start.
73? Bob
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W4 has 1N34A available for it.
1N34A, to keep things original, are sold in many, many places. ?Some places specialize in vintage gear and carry them, and lots of other places too. ? Just do a Google search, or try eBay, etc. but they are available new.
On Saturday, January 20, 2024 at 01:25:27 PM EST, mike bryce <prosolar@...> wrote:
I found some at Jameco. They¡¯re 1N270 diodes
mike wb8vge
On Jan 20, 2024, at 1:20 PM, K6OXN Bob < bobk6oxn@...> wrote:
Just did a search and cannot locate any of the proper diodes. I do have an electronic supply house nearby and they have in stock 93 of the 1N295H diodes.? They are Electronic Expeditors in Camarillo? phone 805-987-3344 ask for Jesse and he might be able to help. They won't be open until Monday the 23rd after 10:00 am PST.
73? Bob
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Re: Drake W4 wattmeter woes...
Clint, PIN diodes are used as variable resistors in attenuators or in AGC circuits.?
For this application, you need a rectifier. Germanium diodes have a lower forward volage drop than silicon. Hot carrier diodes are in between the two. I believe there are some very low forward drop hot carrier (Shottky) diodes that may work. Best, though, to stick with the germanium per the original design to keep the low power calibration something close to "accurate."
73, Bob Loving K9JU
Maryville, TN
On Saturday, January 20, 2024 at 02:33:42 PM EST, Clint VE3CMQ <ve6cmm@...> wrote:
If R1 goes high in value, you will get less signal to your meter.? It¡¯s the only resistor that¡¯s common to both the power ranges.
?
Clint, VE3CMQ
?
From: [email protected] <[email protected]>
On Behalf Of Mike Bryce via groups.io
Sent: Saturday, 20 January 2024 09:21
To: [email protected]
Subject: Re: [DRAKE-RADIO] Drake W4 wattmeter woes...
?
Thanks, Clint,
I remember checking that value, but will re-check it to make sure.
My issue seems to be I can¡¯t get the meter to read high enough. Even with 150W, I can¡¯t set the meter to much over 90W on its scale.
For such a simple circuit, it sure is causing me lots of issues.
Just for grins, I¡¯m going to replace C5 and C4. I only recall once or twice in my life that I¡¯ve found a bad ceramic capacitor, but I¡¯m drawing straws now.
?
"The eye is always caught?by the light, but shadows?have more to say"
On Jan 20, 2024, at 8:40 AM, Clint VE3CMQ <ve6cmm@...> wrote:
?
Don¡¯t forget that R1 is in the circuit.? If that goes high in value, it could throw everything off.
PIN diodes should work well in these meters.? They work well into the VHF range and have low forward voltage drops.? The 1N34 and other geranium diodes were used because they performed better than silicon did at the
beginning.? Things have changed now.
?
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As soon as you sell it you will wish you hadn't. :) 73 -Jim NU0C On Sat, 20 Jan 2024 16:38:16 -0500 "K8CCA" <echapm4@...> wrote: I hardly ever use the vfo, maybe I should sell it lol. -- 73 -Jim NU0C
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Re: Drake W4 wattmeter woes...
°ä±ô¾±²Ô³Ù¡
R1 is right on the numbers¡
The plot continues.
mike wb8vge
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On Jan 20, 2024, at 2:33 PM, Clint VE3CMQ < ve6cmm@...> wrote:
If R1 goes high in value, you will get less signal to your meter.? It¡¯s the only resistor that¡¯s common to both the power ranges. ? Clint, VE3CMQ ?
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Rob Sherwood
Paul Christensen
Greg W9GB
Jim Shorney