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Tube of the Week




 
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KL7OF
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« Reply #50 on: May 29, 2021, 08:21:25 PM »

Nice Dennis...do you have one in your collection?   I like the big spade connections on the base..
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« Reply #51 on: May 29, 2021, 09:30:04 PM »

I count 4 here.  Indeed, unicorns. Wink

Need to get pix.

73DG
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« Reply #52 on: May 30, 2021, 11:45:44 PM »

New week, new tube. Let's go the other direction.  Let's go down in size. Wink
 
The Nuvistor.
 
The Nuvistor was a type of vacuum tube announced by RCA in 1959. Most of them were basically thimble-shaped, but somewhat smaller than a thimble, and much smaller than conventional tubes of the day. Their size almost approached the compactness of early discrete transistors. Triodes and a few tetrodes were made. The tube was made entirely of metal with a ceramic base.
 
Nuvistor tetrodes were taller than their triode counterparts. Manufacturing them required special equipment, since there was no intubation to pump gases out of the envelope. Instead, the entire structure was assembled, inserted into its metal envelope, sealed and processed in a large vacuum chamber with simple robotic devices. It has been said that this process made them more expensive than competing glass tubes.
 
Some Nuvistors were designed to be used in military equipment (some say that this was their intended application, with consumer- and experimenter use being a nice bonus -- and cover story). They were used in the Ranger spacecraft of 1961-65, and interestingly by the USSR in their MiG-25 fighter jet, presumably to harden the fighter's avionics against radiation.
 
Nuvistors were among the highest performing small signal-receiving tubes. They featured excellent VHF and UHF performance plus low noise figures, and were widely used throughout the 1960s in television sets, radio- and high-fidelity equipment primarily in RF sections, and oscilloscopes. They competed with the solid state revolution, and along with GE's Compactron, probably held it at bay for a few years. RCA discontinued their use in television tuners for its product line in late 1971. As of this writing I've not found exactly when their production ceased.
 
Radio amateurs also found use for Nuvistors, mainly in VHF/UHF converters. QST published a flurry of articles using them in the early 1960s. RCA Ham Tips, of course, published several Nuvistor projects, such as a 2-Meter transceiver in its Spring 1965 issue.
 
I first learned of them in the late 1970s, when I found a copy of the 1966 ARRL Handbook in my high-school library.  Therein was a construction project for a portable 420-Mc. transceiver using a Nuvistor as superregenerative detector and modulated oscillator. 250 mW plate input at 45 VDC!  Cheesy
 
Types:
 
* 7586 - First one released, medium-mu triode
* 7587 - Sharp-cutoff tetrode
* 8056 - Triode for low plate voltages
* 8058 - Triode, with plate cap & grid on shell, for UHF performance
* 7895 - 7586 with higher mu
* 2CW4 - Same as type 6CW4, but with a 2.1 V / 450 mA heater.
* 6CW4 - High-mu triode, most common one in consumer electronics
* 6DS4 - Remote-cutoff 6CW4
* 6DV4 - Medium-mu, intended as UHF oscillator, shell sometimes gold plated
* 8393 - Medium-mu, 12.6 V filament
* 13CW4 - Same as 6CW4, but with 12.6 V / 230 mA heater


* 2021-05-31 Nuvistor And Box.jpg (164.88 KB, 418x400 - viewed 281 times.)

* 2021-05-31 Nuvistor Components.jpg (233.12 KB, 560x400 - viewed 292 times.)

* 2021-05-31 Nuvistors And Glass Tube.jpg (136.58 KB, 424x400 - viewed 280 times.)
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« Reply #53 on: June 26, 2021, 11:22:56 AM »

We used to snag the nuvistors out of old color TV sets when they were scrapped. Quite a few older equipments still use them like CEI panoramic receivers and oscilloscopes.
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« Reply #54 on: June 30, 2021, 05:38:09 PM »

Have a couple left in stock, I think.  Common in the 6M AM equipment like the Lafayette  HA-460 of the late 60's.  Still available from some of the tube dealers.  IIRC, replaced the 6AK5 and others as receiver RF amplifier.  Low noise, reasonable gain.  Of course, the noise floor was considerably lower then, so equipment noise did make a difference.
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« Reply #55 on: July 18, 2021, 12:37:52 AM »

How about something that is 77 years old, yet advanced at its time and still powerful for its size?

The week's about up.. but I'd like to highlight the 8025 (8025A, and the 8012 /A having identical curves and ratings)

The 8025 is not common in ham homes, but 'large quantities' are available NOS online for $35 from a large surplus sales vendor so it's overlooked. I bought a box of NOS specimens at an antique radio auction for a song and people don't seem to have any idea what to do with them. It's a nice looking tube!

The 8025 was made by RCA and GE.

It was first used in WWII.
http://www.qrp.gr/technology/linearuhf/High_f.pdf
That might explain the original RCA data having a copyright of 1943, but the datasheet having its release date in 1945.

Plenty of pictures available:
https://www.google.com/search?q="8025"+vacuum+tube&source=lnms&tbm=isch&sa=X
Nice looking, eh?

The 8025A is a small, glass, directly heated 1000V triode with 40 Watt plate, a 6.3V, 1.92A filament, requires bias, and is good for up to 500MHz at full input and reduced input to 600Mhz. The filament center tap is not for connection to ground or to a filament transformer CT, but for an RF bypass scheme to minimize lead inductance.

Its advantages for UHF work are very short and direct grid and plate leads which come out both sides of the envelope.

The 8025/A has 1/4" plate and grid caps and a 'small 4 pin' base, and the 8012/A has grid and plate pins instead of caps, and flying leads for the filament.

It requires forced air cooling for CCS ratings, and is rated for 30W ICAS on the plate with convection cooling. Maximum plate current rating is 80mA according to GE.

Typical AM operation as a class C amp show 22W output at Carrier level.

Data sheets:
1943: https://frank.pocnet.net/sheets/201/8/8025A.pdf  - best info about care and feeding of the tube.
1945: https://frank.pocnet.net/sheets/049/8/8025A.pdf
1945: https://frank.pocnet.net/sheets/049/8/8012A.pdf

It's intended for class C operation and no modulator or linear amp ratings are given.

For those QRP interests and others wanting to play with it at zero bias, the curves show that 400V on the plate results in 22 Watts dissipation. 300V gives 10.5W dissipation.
It could be a good experiment to try as a class AB2 or B amplifier. For its size it seems like an electrically rugged tube.

The thoriated tungsten filament is a plus for that bright glow. I think the plate is tantalum. For forced air cooling, the data sheet only says that air should be directed at the bulb. These are not intended to be supported or stressed by inflexible connectors attached to their plate and grid connections.
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« Reply #56 on: July 22, 2021, 02:59:28 PM »

Hello folks!

How about this one:  the 4-400A. A tetrode, 400w plate dissipation, high gain, low drive.



Data sheet:
https://frank.pocnet.net/sheets/088/4/4-400A.pdf

A place it was used:
The RCA BTA-1R1 broadcast transmitter

manual:  https://bama.edebris.com/manuals/rca/bta1r1/
Found in a fun catalog:  https://worldradiohistory.com/Archive-Catalogs/RCA/RCA-Transmitting-1962.pdf

Some other applications:
600m linear: http://w5jgv.com/4-400A_600M_amplifier/
Old magazine article for an amp: https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1961/01/page33/index.html

There are hundreds of posts on here that mention the 4-400a, and I am certain there are more than a few AM'ers talking on the air on them even now.  New tubes are available, but expensive. Used are in the usual places. I just made arrangements to buy several, with the rest of the transmitter included.....more on that elsewhere.

I'd like to hear from some of the big guns here about their favorite large tube.. Anyone?  Bueller?

Ed K8DI


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« Reply #57 on: July 22, 2021, 09:16:15 PM »


Now there's a Wish Book!  Grin
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« Reply #58 on: July 27, 2021, 12:10:15 PM »

i'm surprised no one had anything to say about the 4-400. Or it's predecessor the 4-250 which makes appearances in the famous KW-1. Not to forget the 4-125 in the 30K-1. The Johnson product line makes full use of 4-250 in the Thunderbolt, 500 and, Desk KW. I believe that most of these rigs went to the 4-400 in later production. There is another giant in the glass family of Tetrode's the 4-1000.  The 4-1000 is truly in a class by itself. The tube just loves Hi voltage 6000 make them smile. It's to bad they are getting expensive 100 bucks used to get you a good tube those days are all gone. I know there is a lot of fellows  on this board that have built plate modulated rigs with these. Not to mention there uses as a linear amplifier tube. Show us some pictures of your 4x1 rigs don't hide those big legged girls.

Johnathan N8QPC
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« Reply #59 on: July 28, 2021, 12:19:27 PM »

There is another giant in the glass family of Tetrode's the 4-1000.  The 4-1000 is truly in a class by itself. The tube just loves Hi voltage 6000 make them smile. It's to bad they are getting expensive 100 bucks used to get you a good tube those days are all gone. I know there is a lot of fellows  on this board that have built plate modulated rigs with these. Not to mention there uses as a linear amplifier tube. Show us some pictures of your 4x1 rigs don't hide those big legged girls.

Johnathan N8QPC


ahhhh..... 4-1000As.  That's my choice for  "Tube of the Week."

Here's Fabio II  -  a working 4-1000A plate modulated construction project.  (125K hits on this BB)     A class C pair plate modulated by a pair.     I also run a pair in grid driven linear. (Rico Suave II)     4X1s get my vote as the coolest and most strapping glass tube for ham radio use.   (Followed by the 813)

http://amfone.net/Amforum/index.php?topic=33816.0


And then came "Quadzilla" .... quad 4X1s in linear service:
http://amfone.net/Amforum/index.php?topic=18616.0

4-1000A data sheet:
http://www.tubecollectors.org/eimac/archives/41000a(52).pdf


The beginning of Fabio II -   and Quadzilla linear running... #3 tube was soft when this picture was taken:


* FABIO II .....JPG (325.5 KB, 960x1280 - viewed 288 times.)

* Quadzilla.jpg (324.31 KB, 1280x960 - viewed 280 times.)
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« Reply #60 on: July 28, 2021, 12:46:19 PM »

Here's some info on operating 4X1s in linear service, GG included:

http://amfone.net/Amforum/index.php?topic=32823.0



This is a rare notice from Eimac concerning GG 4-1000A linear service:

http://amfone.net/Amforum/index.php?topic=18634.0



There is more 4X1 construction info on this BB by doing a 4-1000A search.


Testimonial: In 50 years time, I've bought both new and used 4-1000As;  always ran air chimneys and was never really careful with parameters. I did my share of piss-beating them at times.  Except for one soft tube that I bought that way, I have never had a bad 4X1 tube in all that time.  (same goes for 813s)  


T


* eimac- 4-1000A.jpg EIMAC LINEAR SPECS.jpg (262.76 KB, 600x795 - viewed 258 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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« Reply #61 on: July 28, 2021, 02:18:56 PM »

And, Rico Suave II, the GG pair of 4X1s using regulated screen and grid supplies.   I found that running regulated screen  voltage in GG improved IMD.  The grid did not need to draw much current, which is always an improvement.


http://amfone.net/Amforum/index.php?topic=34543.0


* RICO SUAVE II Pair 4X1s linear.JPG (325.2 KB, 1280x960 - viewed 245 times.)

* RICO SUAVE II.JPG (322.92 KB, 960x1280 - viewed 293 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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« Reply #62 on: October 07, 2021, 01:17:00 AM »

The 5787WA gas regulator. 18 of them came to me in a box of random NOS tubes.

A subminiature gas regulator in a T3 (3/8" dia) envelope about 2" long. It's a ruggedized type rated 98V @ 5-25MA.

These can be had for about $5, and $3 in quantity of >100. 

This little known tube is great for tight spaces and firing is supposedly not affected by incident light.

A possible use in addition to typical shunt regulation duties could be in place of a customary neon lamp for DC coupled vacuum tube circuits and voltage limitation at the front ends of receivers where its higher current ratings could give much increased life. YMMV.


* 5787WA.jpg (157.95 KB, 800x600 - viewed 235 times.)
* 5787WA.pdf (408.33 KB - downloaded 120 times.)
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« Reply #63 on: May 01, 2022, 11:18:00 PM »

The two 866Jr. tubes

The 866Jr. will some times cause an argument. You will find those who insist it has an anode cap, and those who are as vehement that it does not. The same type number seems to stand for either tube. Both glow beautifully in operation because as with many early MV rectifiers the filament is not well shielded.

Both are scaled down versions of the familiar 866. As with other Mercury Vapor rectifiers, it's necessary to use a choke input filter tomget the best advantage from them. The filament power for either is 2.5VAC at a moderate 3A and seem top have similar power ratings. The mechanical arrangement is quite different according to the pictures. It's interesting for those who like to see things glow.


Taylor 866Jr. (also known as the 2B26)
No anode cap. Anode is pin 2.
1250V RMS plate voltage
250mA per pair in FWCT choke input circuit
https://www.nj7p.org/Manuals/PDFs/Tubes/Taylor-1939.pdf

This catalog page claims 5000PIV and 500mA peak plate current!
http://w5jgv.com/downloads/taylor%20tube%20catalog.pdf

--------------------------------------------------

Hytron (Hytronic Laboratories) 866Jr.
Anode cap on top of the envelope.
1750PIV
250mA peak current
125mA average current
A pair in a FWCT rectifier circuit with 1250V RMS per anode can supply 1125VDC @ 250mA
http://www.r-type.org/pdfs/866jr.pdf




* s-l300.jpg (48.23 KB, 421x301 - viewed 95 times.)
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« Reply #64 on: May 02, 2022, 06:19:12 AM »

I have some regulators that are smaller than those 5787's. They are only 2 wire and were used on the +100VDC rail of the HP-141T. From what I have (recently) learned, these are responsible for taking out the fuses on the 8552 and 8553A sub-modules. They don't ignite fast enough and cause the regulation circuits to crowbar making the fuses blow. I was advised to replace it with a couple of zeners and problem now solved!
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« Reply #65 on: September 10, 2022, 02:48:09 AM »

The 808 comes to mind. A friend has two push pull pairs, one pair as a class C RF amp using plug-in coil with link of course, and one pair as a modulator using a BC-610 transformer. These are running about 1500V. One cool thing about them is the beautiful globe-shaped envelope, "G22" bulb. The bulb contains the guts and is built like a globe sitting atop a cylinder, and the 7.5V/4A thoriated Tungsten filament, which provides plenty of light for admiring the RF deck area. Both grid and plate caps are used.  He never abuse them, so normally the RF power is around 130W (carrier) despite two tubes in push pull. The modulator pair are driven by the usual reverse-connected audio output transformer, in this case a 20-30W hi-fi unit. Unfortunately a few audiophools have been defiling the 808, but it isn't too common.

https://frank.pocnet.net/sheets/049/8/808.pdf

Did I mention it's a beautiful tube?
https://commons.wikimedia.org/wiki/File:RCA_%E2%80%99808%E2%80%99_Power_Vacuum_Tube.jpg
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« Reply #66 on: September 10, 2022, 12:52:01 PM »

Here are some links to pics of that 808 amplifier on 160M, built in period appearance by Dennis Brady W5FRS. Note all the crystals - -the exciter/osc are not shown but are also tube types. I believe this is from before he included AM in the hobby. Pics of the 808 modulator follow.

"In the CW room, This push-pull 808 RF amplifier operates class C and is used for CW work on 160 meters. The plate coil assembly is a BC610 low range coil, designed for 2-4 MHz. The tank coil is resonated by a dual section 180pF air variable with an added 50pF doorknob across it to center the band. The doorknob stays cool in this application. (the capacitances stated don't include the plate capacitances of the 808 tubes.) The output is easily 150 watts with no color on the classic plates."
https://bunkerofdoom.com/w5frs/PP_808_160M_amp1.JPG
===============

808s glowing in the dark
https://bunkerofdoom.com/w5frs/PP_808_160M_amp2.JPG
===============

808s RF deck. The grid coil section is off the lower edge of the image and can't be seen but it also uses a plugin coil, IIRC an 807 base and socket and self supporting coil and link.
https://bunkerofdoom.com/w5frs/PP_808_160M_amp3.JPG
===============

808 modulator chassis:
https://bunkerofdoom.com/w5frs/2/100_9963.JPG
===============

808 plate current meter swing 'Calling CQ' video:
https://bunkerofdoom.com/w5frs/2/100_9965.avi
===============

lusty pr0n of the 808 modulator:
https://bunkerofdoom.com/w5frs/2/100_9980.JPG
https://bunkerofdoom.com/w5frs/2/100_9983.JPG
===============

The metering panel of the modulator:
Left to right: grid current, plate current, plate voltage, bias voltage, filament voltage.
https://bunkerofdoom.com/w5frs/2/100_9962.JPG
===============

Thats all folks!







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« Reply #67 on: September 10, 2022, 01:06:11 PM »

Legend has it the General Electronics (not GE) were better than the RCA's.

I've used both, and so far that is true.

73DG
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« Reply #68 on: September 20, 2022, 10:19:22 PM »

Here's a nice one, picked up at an auction. This is the National Union 2203, an Monatron tube.

It provided a test pattern for the alignment of TV cameras, monitors, TV sets,  and the like. This type of tube was popular with TV amateurs and hobbyists because it was much lower in cost than the RCA version, and required only a simple oscilloscope-like electronics circuit compared to the CRT inside the high-end, complex RCA TK-1.

This 2203 tube seems to have some visual issues, but as of yet I don't know what it will look like when making a TV picture. I don't know who the two people are. In those days one could order just about any monascope or monotron tube with one's choice of imagery and the factory would apply it and make the tube(s). The tube is identical to the National Union 2003 CRT except for the image plate and 'plate cap' instead of a phosphor coating.


About the RCA Monoscope Camera TK-1 and its 2F21 tube:
We have all seen the famous monochrome RCA test pattern with the Indian Chief artwork. It was generated by a special CRT type 2F21 inside the TK-1 Monoscope Camera (test pattern generator). The image was intended to allow resolution and linearity checks on TV receivers, and indeed served as the gold standard for test patterns at many TV stations before the days when similar video test patterns were made possible by technological advancements.

The Indian Chief artwork contained carefully formulated gray shades and details intended to include subjective yet technical information within the pattern of lines, wedges, and circles. The entire pattern was placed on a metal plate and a terminal pin extending through the CRT face provided the output signal for the TK-1's video amplifiers. Sync and blanking was added and shipped to an SO-239 at the standard 1V peak to peak into 75 Ohms. I am currently doing an electronic restoration of a TK-1 for a friend. At this point, a surplus HV power transformer has been found and ordered and we believe that his RCA Monoscope tube is good.

A low voltage power supply (280V@300mA/-3V@1A, ) must also be found or constructed, but first heat will be done with laboratory power supplies, so that the tube can be checked before undertaking that considerable task. In case anyone has an RCA model 580-C (MI-21523-B1) power supply, that is the proper unit for the TK-1. Close regulation of all voltages including mains power is essential.

I can add only one image per post for some reason.


* IMG_3631.JPG (77.4 KB, 1223x278 - viewed 25 times.)
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« Reply #69 on: September 20, 2022, 10:20:22 PM »

The image on the target plate


* IMG_3635s.jpg (196.32 KB, 1600x1348 - viewed 21 times.)
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« Reply #70 on: September 20, 2022, 10:22:43 PM »

Who can these be? It's my impression that this is the standard non-custom tube.


* IMG_3634scs.jpg (703.87 KB, 1500x985 - viewed 21 times.)
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« Reply #71 on: September 21, 2022, 09:06:03 PM »

i'm surprised no one had anything to say about the 4-400. Or it's predecessor the 4-250 which makes appearances in the famous KW-1. Not to forget the 4-125 in the 30K-1. The Johnson product line makes full use of 4-250 in the Thunderbolt, 500 and, Desk KW. I believe that most of these rigs went to the 4-400 in later production. There is another giant in the glass family of Tetrode's the 4-1000.  The 4-1000 is truly in a class by itself. The tube just loves Hi voltage 6000 make them smile. It's to bad they are getting expensive 100 bucks used to get you a good tube those days are all gone. I know there is a lot of fellows  on this board that have built plate modulated rigs with these. Not to mention there uses as a linear amplifier tube. Show us some pictures of your 4x1 rigs don't hide those big legged girls.

Johnathan N8QPC
GG 4x1 with russian vacuum relays switching the taps on an edge wound gates coil


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« Reply #72 on: September 21, 2022, 09:12:18 PM »

more


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« Reply #73 on: September 22, 2022, 11:17:03 AM »

Hi Steve -

I've rarely seen Russian vacuum relays used as a band switch. Very cool.  I can imagine the faint "klunk-klunk" sound as you turn the small rotary switch on the front panel.

Is there input cathode tuning... maybe the pictures didn't show it ?   If not, highly recommended to pick up another -5 dB of 3rd order IMD improvement and be easier to drive..  better exciter match. An L/C input network works well.  (small roller inductor in series with a paralleled 365-365-365 type variable cap to ground will match anything)

That 6500VDC ++ HV will really make it sing.  How effective is the blower and how loud is it?

Looks like an easily servicable rig.

What bands does it cover?  

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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« Reply #74 on: September 22, 2022, 04:27:29 PM »

Hi Steve -

I've rarely seen Russian vacuum relays used as a band switch. Very cool.  I can imagine the faint "klunk-klunk" sound as you turn the small rotary switch on the front panel.

Is there input cathode tuning... maybe the pictures didn't show it ?   If not, highly recommended to pick up another -5 dB of 3rd order IMD improvement and be easier to drive..  better exciter match. An L/C input network works well.  (small roller inductor in series with a paralleled 365-365-365 type variable cap to ground will match anything)

That 6500VDC ++ HV will really make it sing.  How effective is the blower and how loud is it?

Looks like an easily servicable rig.

What bands does it cover? 

T
Hi Tom.  The relays are pretty quiet.  They make a click.  I also use one to switch in a padder cap for 75 M.  I use a tuner for the input..  The blower is very effective even when running AM Its a Grainger unit and I can hear it running .I forgot the CFM rating...I've used them before   Mic doesn't pick up the blower.  The amp covers 15M-75M.  Some of the pictures were taken during construction and a few things have changed.  The 4-1000 is one of my favorites...I have REALLY piss beat a few of them and they hold up very well. 


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