Reconditioning a 1973 Wavetek 3000 RF Generator

While working on the design of my first receiving loop wideband amplifier, I decided I needed some kind of RF generator to do bandwidth tests. So I went to Ebay and did a search and stumbled on a familiar sight – the Wavetek 3000. And it was cheap too. One was only $120. It was described as “working but untested” which I took to mean, that at least one of the front panel lights come on when power is applied. This unit can generate RF from about 500 kHz to 500 MHz, and during its time it was known for its spectral purity and stability. It has a true digital synthesis design, but is designed using a mixture of discrete transistors and basic TTL IC’s. So, I bought it! I figured, what’s the worst case here? I’m a qualified electronics engineer and should be well able to fix anything that’s wrong with it. Optimism never hurts I guess, but of course, when it arrived it was fairly useless — on some settings it did indeed produce a waveform, but highly distorted and nowhere close to the frequency dialed in on the front panel.

To make a long story shorter, I went through it and managed to get it working quite well. I’ll summarize the work I did below, but before getting into the details, here’s a photo of it on my shelf in my lab. It looks good there.

Construction of the unit is a wonderful example of discrete RF design, with most circuitry built by hand using point-to-point techniques in hard tin “cans”. I thought it was handy that Wavetek printed the can interconnect diagram right on the inside of the top cover:

After doing a rough diagnostic on the unit using its schematic, I found that the signal disappeared at the “Output amplifier” can designated as M10W. I pulled out that can, and found inside it a circuit with an obviously cracked and dried-out 10 uF aluminum electrolytic capacitor (C32). Looking further, I found others which were either badly reduced in capacitance or were leaky. In addition, to my horror, the IC’s were socketed, with the point to point wiring done to the socket itself. So, I decided to go through the entire unit and do two things: (1) replace all electrolytic capacitors, even the tantalum ones, and (2) unseat and reseat each socketed IC, to abrade the pins and hopefully reduce the risks of loss of contact due to corrosion.

The cans have pins on the bottom, mostly used for power connections, and are connected at the top by a network of SMC cables. At this point I want to remind everyone that there are 3 types of miniature RF connectors: the very familiar SMA connectors which are commonly used today, the lance-fit SMB connectors, and the smaller and rarer SMC connectors. While working on the unit, I found a frayed SMC cable and had to order a replacement from an Ebay supplier who made one to order. This photo shows the tops of some of the cans, and their SMC cables.

Here’s a look at some of the capacitors I removed and replaced:

Below, a look at a sample can, the M29 module. This shows the point to point and socketed IC construction techniques. At the bottom left is an original 10 microfarad capacitor which I later replaced. Additional wiring is on the other side. In many modules, a sub-can consisting of smaller tin boxes or walled-off sections are used. The Wavetek 3000 is a wonderful lesson in how to push the performance of point to point discrete component design right to its limit.

Below is another example module, M33a, showing some of the sub-can construction. Note the two tiny component areas at top right. These were all hand wired of course. How long do you think it must have taken for the assembler? This kind of construction requires a high skill level of the assembler. These skilled point to point assemblers undoubtedly lost their jobs as this kind of assembly converted to PCB, ASICs, and offshore suppliers. So this is a relic of a different age. At the lower edge (red arrow) you can see a place where I hand wired a replacement 100 uF capacitor, using a surface mount component, plus leads.

Below is my M32A unit. You can see that the MC4044 and the Eprom both have date codes of 1982, but someone much later put new 74S196 IC’s in the sockets because they have data codes of 1990. Many of the linear IC’s have date codes of 1978.

To test the repaired unit, I used my ham radio (FTDX5000) to evaluate the accuracy and spectral purity of the sine wave at various frequencies. The accuracy is excellent — it is within about 150 Hz of the exact frequency on most bands. The amplitude stability is good too, though some noise is still visible when using a scope. Below, I’m checking the noise level with my oscilloscope on the 10 mv scale, comparing a channel looking at ground (red) with one looking at the signal (blue) — the noise seems nearly the same amplitude, so the Wavetek is not contributing a large amount of noise. (Scope: Picoscope MSO 5244D.)

There is some amount of phase noise, causing the frequency to contain a FM signal with about a 100 Hz width. I think this might mean that there is still a problem. But as is, the unit is perfect for sensitivity and bandwidth measurements, and I’m really happy with the result, and I’ll be using it when I do my redesign of the wide bandwidth amplifier for the receiving loop antenna.

My thanks to VK3ZZC, Ralph in Australia, who gave me troubleshooting advice by email. Here is his experience:

In response to your question,  nearly every single black tubular electrolytic either was a dead short , or quickly became one once power was applied. The truly wonderful news is that a couple of them are hiding inside tin cans…inside tin cans…all lovingly soldered shut.  The part of the implementation that truly caused me to ask , “how could anyone be so daft”, was discovering inside 3 nested tins  one of the divider chains, counter ICs in sockets ! At least it was a proper little pcb…but sockets…in a space that was utterly unreachable  without destroying the unit. As you know, sockets are always totally reliable.  It was this that brought about the death of my Wavetek.  It had a stable, noise free output…utterly unrelated to the thumbwheel setting !

I do not understand their fixation on the horribly expensive point to point wiring,  in an era where PCB’s were a well established technique. Just look at equivalent contemporary products  from HP.

The one other thing you must do,  check the +/- 18V regulators.  The series pass transistors will fail as a short. Pre-emptively wire in some sacrificial zener diodes to protect the rest of the unit.

 I still think that the electronic design of the wavetek 3000 is sublime. The implementation ,however, was a farce.

If you have a Wavetek 3000 I’d be glad to help you out if I can. Leave me an email. Here are the two service manuals I located on the Internet:

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Automatic Half-Duplex WebSDR Audio Switch for Yaesu and Similar Radios

Band conditions on 75M lately have been terrible. So bad, that our long-time scheduled 75M SSB meetup of our four hams on the West Coast can’t work radio-to-radio due to high levels of noise. Also, propagation seems to favor distant stations over nearby ones, due to the inability of the ionosphere to reflect a near-vertical incidence wave at frequencies over 3 mHz.

We have been forced to use the Internet to make up for our inability to receive the distant station. One way to do this is to connect via Internet to a WebSDR page. A WebSDR is like a remote receiver that you can control yourself. Once you are connected to it, you specify the frequency and mode, and you can listen to the demodulated audio on your computer. By picking a WebSDR which is located in an area that your distant station can transmit to, you can listen in on your station even if the noise entirely drowns them at your own receiver. So this is what we do, when it’s necessary.

Some may say this is not how Ham Radio should work. That using someone else’s receiver, and the Internet, is cheating. Perhaps that’s true for contests, but networking with other radios in order to break thru propagation blocks is just another part of the hobby’s advance through the years. And it’s only fair — if Ham radio is a backup for the Internet, then the Internet should be the backup for Ham Radio. Right?

But manufacturers of modern transceivers haven’t kept up, of course. Our problem is that if we are listening to the WebSDR on our computer speakers, and we begin speaking into the microphone, we get feedback started and an embarrassing buzz or howl ensues. So to go from listen to speak, we have to shut off the computer audio at the same time we activate the push-to-talk button. It can be awkward and it invites mistakes, especially since it usually involves a mouse click. Then we have to reverse the process. Being forced to switch between sending and receiving is sometimes called “half duplex” operation. So the hobbyist’s answer is — design and build a device to switch between computer audio and radio audio. So here is such a box. Before we go too far I want to apologize for the shoddy construction methods and the reuse and abuse of old parts — I made this out of stuff that was within reach. If you make a version of this, yours can be pretty and professional if you like.

Rough interconnection diagram
Detailed Schematic (click for full size)

Operation is simple. There are two front panel switches, one marked “Radio” and the other “Computer”. As wired, turning on one or the other connects that source to the output. Turning on neither switch connects the computer UNTIL the radio goes into transmit mode, when it switches to the radio automatically. This will be the normal mode when listening to a conversation via the WebSDR. (Note: turning on both switches forces the computer to the output.) If you choose to use headphones, plugging them in will shut off the audio to the speakers. There is an output for an oscilloscope, to monitor the audio, if you like. Here are some photos.

View of the chassis rear.
View of the front. This was before the circuit board was screwed into place.
The LED is the little round indicator at the front top.

Finally here is a photo of the finished unit snuggled up alongside my Yaesu FTDX5000MP radio. It operates flawlessly so far. If you need to use an Internet device to receive sometimes, you need one of these too. Write me if you have any questions.

Hams Want Spectrum Displays! The Solution is the Panadapter. (SDRPlay RSPdx/RSP1a/RSPduo and Yaesu FTDX3000)

Yes! Hams have made it clear that they want spectrum displays on their radios. So what did HF receiver manufacturers do? They included REALLY BAD displays in their new receivers, dooming those designs to quick obsolescence. Ask yourself — would you like a display like this?

“Spectrum” display on my $1800 Yaesu FTDX3000.

Or, would you like something more like this?

SDRuno software main control and spectrum display.

The latter display is the SDRuno software running on my Lenovo Yoga Laptop. The key is the inexpensive black box “SDRPlay RSPdx” which can do two things at once: (1) Mirror all settings of common, modern HF transceivers on the PC screen, allowing control from the PC, and (2) analyze the RF input to the transceiver, displaying it as a spectrum, and optionally demodulating it into whatever mode you need: CW, SSB, RTTY, etc. All this for about $199, assuming you have a laptop and transceiver. Here is a nice Youtube summary of how to set it up.

My setup. Left side: the RSPdx unit. Bottom: the Yaesu FTDX3000 transceiver. Top: the Lenovo Yoga laptop, in reversed orientation with downward-facing keyboard. I use a bluetooth keyboard/mouse.

It’s a trend, and as I said, conventional HF base stations, even with touch screens showing a poorly-displayed spectrum scan, are doomed to becoming obsolete. As an engineer, I feel certain this is happening, and I needed to rant a little about it. So then, where is this going? It can only go in two directions, and of course, it will end up going both directions at once. One direction is the premium transceiver with LOTS of physical dials, buttons, and direct hands-on control for the ham operator who wants the kenetic, haptic, and tactile experience that only old-school equipment can deliver. (Example: the FTDX5000) The other direction is the box-plus-pc solution in which the ham relies on their computer for ALL control and display. And it’s here already: the Expert Electronics SunSDR2-Pro transceiver, the ultimate in PC transceivers. I’m not in the market myself, but my message to other hams is this: FORGET the Icom 7300, it is a Frankenstein’s Monster, a patchwork of concepts that you love today but will not stand up to time’s progress well. Forget FlexRadio, whose quality (and price) is sky-high. Even my FTDX3000 will look sad ten years from now. At least I can hide it and use the computer interface for nearly everything. If you are like me, the $199 SDRPlay RSPdx box will allow you to convert your modern receiver to a fancy panadaptor spectrum display, as I did above. But seriously, check out the SunSDR2-Pro, and especially, check out those upcoming PC-only transceivers that should be coming out in the near future. They are the new direction. The next great radios will be boxes that you put in the corner out of sight – or boxes you can install at the top of a mountain a mile away – yet control with your laptop while relaxing in your hot tub.

Ad for the SunSDR2-Pro by the Russian company Expert Electronics.

I Modified This Vibroplex Bug For Slower CW Speeds

Here is the key I got used from Ebay. It’s in perfect condition.

Years ago, I only used a straight key for CW. But this time, I decided to treat myself to a “Bug” – a semiautomatic key. This kind of key uses an oscillating pendulum to generate clean, well formed “dots” but the longer “dashes” are still fully manual. The Bug was originally designed for expert Morse operators, to reduce the Repetitive Motion injuries from operating a key all day, and to make it easier to send at speeds over 20 words per minute. However, there is a real need for the key to work reliably at much slower speeds too. The original key included an optional “swing weight” which you can see as an arm connected to the pendulum, which can be moved to adjust the speed up and down, but using the swing weight alone the key speed is 20-50 WPM, still far too fast. It’s not too difficult to see that, being a simple pendulum, adding even more weight should slow it down. The question is, how to add that weight?

I started by cutting a short piece from a copper bar, and drilling a hole to fit it onto the pendulum shaft. This allowed speeds down to about 15 WPM. However I wanted to go really low. So I cut a short piece of 0.195 OD brass tubing and inserted it over the original pendulum shaft. It’s held in place by light friction only, with a piece of wire insulation chosen to provide the right fit. A piece of 10-32 brass threaded shaft was pressed into the tube making a permanent piece. Brass nuts then can be added or subtracted. In addition, the original copper weight was given 10-32 tapped threads allowing it to be added as well. This brought the slow speed down to about 7 or 8 WPM. The entire assembly is now capable of speeds from about 7 to over 45 WPM depending on what weight is present and where the swing weight is positioned. Its 4 configurations are: original with swing weight (20-50 WPM), with extension (12-22 WPM), with big weight on pendulum shaft (15-25 wpm), or with extension and weight both (7-16 WPM).

The key is a delight to use! I’ve been warned by some other hams that adding this much weight to the pendulum might stress the bearing assembly, but I’m not too worried about that. The force needed to hold the pendulum horizontal is indeed higher, and that means the friction is higher, but I think a tiny spot of heavy lithium grease might insure that wear on the bearing is tolerable.