The Heathkit VF-1 VFO was a low cost and very early kit, that freed the ham from the restrictions of crystal control. Very few items in the Novice era can elicit so much commentary as this gem. Let's bring one back to life.
I bought a couple of these - one copper plated and the other not. The silver one was completely intact but worked very poorly. I took out the tuning cap and cleaned the rotor rounding clip, which was badly tarnished. In the process, I found a never-soldered joint where the band 1 capacitors go to ground. I’ll bet that drove the original builder and any subsequent owners nuts! I bought the copper one on eBay. All the caps were replaced with crazy values. I decided to completely disassemble this one and build it from the ground up with new components following the original instructions. It was a lot of fun! The tuning cap ground spring needed cleaning on this one too. The 160M inductor slug was butchered, but I Macgyvered a replacement using a long brass screw and a ferrite bead swiped from a discarded VGA cable. Worked like a charm! For both, I decided to replace the OA2 with a pair of 50V zener diodes in series with a 22k resistor to get the screen grid voltage to a steady 105v. It drops the heat a little further too. As for the plate voltage, Heathkit’s specs were 250-350 volts dc. Someone told me that electron-coupled plates can run fine at 3 to 3.5x screen grid voltage. And my PS is at 310 under load, so it’s just right. I also used stiffer wires for the RF circuit to improve the mechanical stability. Both VF-1’s work very well! I think the rotor clip tarnish was a huge problem for mechanical stability. Solve that and you’re a third of the way home. Solve chirp with tube substitutions and steadier screen grid voltage voltage? That’s another third. The heat reduction address drift, the final third.
Excellent video. I was amazed you actually tamed this unwieldy thing. I'm the guy with the videos showing how to solid state the Vf-1 (and HG-10), making it standalone by adding a 24v power supply and LED dial lights. Also, by converting to direct drive and eliminating the vernier feature. Also, by changing the wafer switches to toggle switches. There are a lot of choices. I don't think we should be throwing them away. Another ham actually sells a plastic replacement dial which is very nice. There are so many ways to continue to use them rather than just giving up and tossing them into the trash. By the way, I also have one of the old Leader scopes which I really enjoy using. Please be sure to change out all the electrolytic caps if you have not already done so. Us old timers are a dying breed and I'm glad to see you are staying in the game. (I'm 79 now). The younger guys can't figure out what to do with tubes. Times have changed.
I bought one in very nice physical shape. I made a power supply for it and it worked okay. Yes, it was chirpy and a little drifty. I tried tube changes but it didn't really improve much. But the real problem was mechanical instability, however, and yesterday I decided enough was enough. I tore it apart to get to the main tuning capacitor, assuming (correctly) that the rotor grounding spring was tarnished. I cleaned it up and started reassembling it, only to find a *never-soldered* joint from the 10/47 uuf VFO capacitor pair to the ground lug. For over 60 years, this poor VF-1 has been torturing both owners and the stations with whom they tried to communicate, all due to one missed step in the original assembly! It's going back together now and I should be a much happier ham in a few hours. I think the VF-1's poor reputation has as much to do with assembly flaws as anything else.
I have just run some drift-tests with my VF-1 here, Mike, and the results....once it is warmed up...are literally amazingly good. I'll send the results to you via e-mail soon. Warm-up-drift is "not good" in my opinion, but is still better than some other VFOs of the period. I insist that the "bad press" the VF-1 has received from some users is due to several factors, one being poor original construction, but another being that some users are not aware of the factors which can cause it to sound and work badly. I modified my present VF-1 to enable me to switch between blocked-grid and cathode keying and I use it with my HW-16. Lastly, I used a VF-1 many years ago as a transmitter for short ranges. I remember receiving a 599 report on 40 meters from a station in Idaho when I was living in Missoula, Montana. But band-conditions then were far, far better than they have been in recent years. vy 73, Mike.
I've still got three of these. One is a "parts" unit, the other two I refurbished electronically and wired one-each for the two keying modes. I use them variably to set frequency on transmitters and transceivers. Having two prevents all the re-soldering anytime a different keying mode is called for. The VF1 may be older than the HG10 external VFO, but the VF1 is far more stable. Matter of fact, if either of mine are warmed up for a full hour there is no drift. Actually in my "novice era" VFOs were banned. We were limited to 75-watts and crystal control. Using a VFO on HF required a General license as a minimum.
correct....think it changed in 1972....then a Novice could have VFO Control....DX-40, and an s-53a and a dx-160 for me....handful of crystals, a knight VFO...an old elmer rigged it up for me to work with the DX-40....1980....then I got an HW-8 in 1981....back in the day...dx with old tube rigs, and QRP....had a horn button for a key once in the early 80's...it worked...
Nice job...look forward to your DX-40 video (my first rig BTW too). I'm planning sacrilege however, I plan to remove the guts of my DX-40 and build it into a Drake 2-B receiver case to create the matching transmitter that Drake never built for the venerable 2-B. The Radio Gods may never forgive me.... 73 - Dino KL0S
Nice job Michael! I'm looking for a VF-1 to go on the air for SKN coming up on Jan 1 but doubt i'll find one in time. So the DX-40 station will go on the air rock bound. You can see the station on my QRZ page. 73, Paul W1SEX.
Great job you did selecting the different tubes. I just finished rebuilding a Drake TR-6 and select tubes also. I have subscribed and will watch more. K6LIG
As you mention it does seem as though the supply may have been the problem with the VF-1. I had one back in 1967 just after receiving my General, but used it with a custom supply for the VFO that then drove my homebrew TX (as a kid I couldn't afford a DX-60, but it appears that worked to my advantage). Other than needing to let it become reasonably drift-free after say a 20 min. warm-up, I had none of the reported hum, chirp, click, or other issues. I suspect that the reported chirp had to do with the huge variation in the plate voltage when keyed when used with a Heathkit TX, whereas with the custom supply the voltage was reasonably constant.
I think you are right on the money with this. The power supply is a first order influencer, and Heath was all about utility and "free" features in the competitive entry market for the young ham.
@@MIKROWAVE1 Just as a fun "exercise for the reader" type of issue, identifying the exact source of the chirp isn't immediately obvious to me even with the shift in the supply voltage. My best guess is that the space charge in the grid-cathode region, which is affected by the bias, would change the effective Cgk. However there's nothing in the 6AU6 datasheet to confirm this. Also, the worst case effective output resistance of the 0A2 is 240 ohms, and so the screen voltage variation may actually have more effect on that space charge than that of the much larger plate voltage variation. That same mechanism might also explain the hum. As an experiment it might be interesting to patch a bench supply into the 0A2 socket to see if that resolves a chirpy VF-1/DX-60 combo. It makes no rational sense, but to this day that green display triggers an extreme sense of freedom in me. As a novice I was rock-bound to 7.181 MHz, but with the VF-1 I could go anywhere! 73s and thanks so much for the video, Roger NC6G
Ah. A nice Heath/Ham fix for the day while traveling. Brilliant. The power supply you used, and obviously constructed, in the HR-10 station at the end of the video is a very attractive design. Did you produce a video about that power supply? It appears SS? (Nothing glowing on top). Thanks, Wes W3KW
This Heathkit VF-1 is substantially similar to the Johnson Viking VFO-122 I used with my DX-60 as a novice .(and still have both). Same 11m coverage, Same 40 & 160m fundimentals, as well as having dials split between two halves of the dial for 40m vs 160 fundimental bands. The main tuning cap in both is not a split stator as your video seems to say. Rather a continuous rotation type, and the plates mesh CW on one band and CCW on the other, that is why some of the bands tune backwards. The circuit is virtually the same, same tube complement even. The Johnson has a tapped output inductor vs. the Heathkit having two separate inductors. The only obvious difference is mechanical: Heathkit used a planetary ball (? guessing?) vernier drive, and a backlit dial, while Johnson used a friction reduction drive on a white painted metal dial. The Johnson had the "off" function integrated into the band switch, while the HK had a seperate switch. The Johnson had a bit of an art-deco look, while the HK looked a bit more techy. The Heathkit looks a bit nicer, IMO, but I wonder if being able to rest your hand on desk makes for easier zero-beating on the higher bands where the tuning is bit quick. I eventually converted my Johnson 122 to solid state (pentode replaced with cascoded 2N3904 over a MPF-102 JFET) in an attempt to cure drift and yoop. Quadupled the 6.3VAC supply to power it. (not enough drive to DX-60 when doubled to run a 2n2222 instead of 3904) Pretty well ended the drift, but it still yooped about the same. Eventually I ended up adding a 2N3906 to switch in a few pF when key-up, thus lowering frequency a few KHz so I wouldn't hear the back-wave when receiving. That way the osc. ran all the time, and didn't yoop when keyed, and of course no noticeable drift. Of note is that both of these VFO's can be touchy on the output cable, both length and type...well, actually, capacitance to resonate with the output L is the critical factor, so you can run a bit more cable length if you use RG-59 instead of RG-58. The Johnson wants 36" of RG-59.
Just some final notes: If anyone wants to try a Johnson 122 with a DX-60, or 40 the octal plug needs to be rewired...the pinouts are totally different. The same applies if you want to run a Johnson Tx with a VF-1. Also, both the J-122 and VF-1 are cathode keyed, so they need to be converted to grid-block keying for the DX-60.
Hi Mike Great video. Did you feed the vf1 with 350v through the dropping resistor? Also, the rf output could just be loose coupled to the counter right? My old fluke frequency counter has an antenna in the A position, is there enough rf to be picked up? Thx Frank
The DX-40 has a 15K or a 20K 10W resistor ( depending on the schematic you find) from the HV to the accessory socket. This crude method allows the VF-1 to be powered at a safe voltage between 250 and 300V when it draws 15 to 20 mA. Obviously the plate voltage goes all over when you key. But the regulation on the screen saves the day. Any good modern counter will be sensitive enough that you do not need to direct couple through an attenuator like I did.
Thank you, Michael. You are too kind. I think you have done more for our community than I ever have. I'll have a few more comments later. Good job!! vy 73 for now.
Thanks for another fine video that was enjoyable to follow! Since the front panel was curiously unpainted and unlabeled, I kind of wonder if your VF-1 is an original prototype. Nice job on the new front panel. Is that a printed label you made? Looking forward to seeing it paired with the DX-40! 73, Jack WA6KYO
Ha - dunno about that! But I can tell you that I made a contact with it! To West Bloomfield MI - 725 Miles with less than 10 mW to the Inverted L. Perfect conditions at 10AM on Sat.
11:00 - Maybe you should have set that frequency counter to a shorter gate time. Adjusting would be somewhat easier with a higher display update rate and 1Hz resolution with that simple dial isn't really needed.
Hi Michael, excellent video, Thanks. One question... How did you do the artwork for the front panel of the VF1? Was this a decal or something else. Looked factory fresh ! 73, Glenn WA4AOS
Mike, if folks are interested, Bob Eckweiller's Heathkit articles can be found on the Orange County Amateur Radio Club website - w6ze.org - on the left hand side under the "Heathkit Articles" link. Bob is a great guy and Heathkit guru. Definitely worth a look! de k6whp dit dit
I have 5 VF-1s so I could hook them up in parallel and get 65 milliwatts or hook them in series and get 5X the frequencies. Most people don't have separate power supplies, let's see you make it not chirp powered by the DX-40.
