Rebuilding Time

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This month Lee Aldridge G4EJB gets as far as persuading his Howes transceiver to work again.

 

This month Lee Aldridge G4EJB gets as far as persuading his Howes transceiver to work again.

 

About time to start investigating the old Howes 20m CW transceiver, Fig. 1, that’s what I said. I had been reluctant to look at it for a while. I think the lack of access to proper test equipment was one issue. Secondly, it was about seven years since I’d had the lids off and even though it had been nicely built, I had no idea if it had been switched on, aligned or tested. Could I fix it if it was faulty? That was really a large part of the reluctance. Anyway, with the modicum of success of the previous projects, I decided to have a go.

To cut a long story short, even though all appeared to be fine, certain issues had to be addressed. There was receiver audio instability and hum, the VFO was drifting and generating hum of its own, the buffer board was not helping the cleanliness of the VFO and didn’t function, the S-meter board didn’t work due a component that hadn’t been soldered at one end, a couple of preset pots were a little fragile (meaning that I broke them), the transmitter board didn’t function because, again, a component hadn’t been soldered at one end. But apart from that, whoever built it was probably rightfully proud of their accomplishment.

I found it best to eliminate one problem at a time. While working with this type and age of technology, I had read through some of the original C M Howes notes on construction and also found a useful article on direct conversion receivers:

https://tinyurl.com/y96bxyh7

(The article appears to have originated from RadCom and accredited to Nik Hamilton G4TXG).

Using the original construction notes, substituting screened audio cable, isolating and screening the VFO board, upgrading frequency critical components in the VFO, adding a few electrolytic capacitors to DC supplies on boards, rebuilding the buffer to feed my frequency counter, improving earthing and adding illumination to the S-meter − that’s the bit I excel at – provided me with a working and amazingly stable 20m CW transceiver.

 

Testing

I built an RF probe, Fig. 2, and learned how to calculate power from the resultant DC voltage reading on my DVM. One useful article I found online was:

www.ab4oj.com/test/pwrmeas.html

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I then connected up my economy SWR bridge with a dummy load and with my transmitter on a set frequency, I made a pencil mark on the bridge to indicate 2W full-scale reading. Not quite the most accurate measuring equipment but it was as good as I could do.

There were still a few concerns such as the potential for transmitter-generated harmonics so I built a 20m CWAZ lowpass filter courtesy of the designs on the G-QRP club website:

www.gqrp.com/technical2.htm

Despite some very cold evenings in my shed, I was delighted with the outcome but still wanted to sort out a few more issues with the radio before I started using it. I thought it required semi-break-in keying and sidetone, while a preamplifier might help liven it up and reduce some of the VFO radiation on receive. Ah yes, a bit more work. I think I was still finding excuses for not getting my Morse back up to speed. At some point it would become apparent that if I was going to make use of my licence with the equipment I had, I would have to address my reluctance.

But for now, I had a working radio in a decent enough case that, yet again, I can listen to while building, wait for it, a Morse key.

 

Morse Keys

There are times when you wish you hadn’t thrown something out even though it was 40 years ago! My old Morse key was with a Wireless Set No.19 and after getting nowhere with the Set No.19, I removed the key from its metal case and mounted it on a piece of wood. Where is it now?

I had looked at some of the very nice Morse keys for sale, looked at the price of second-hand Morse keys, and looked at the very smart iambic keyers and PIC-based keyers. I was still shaking my head. So how am I going to build one? I saw some very innovative keyers detailed in a number of publications but the photo that caught my eye was one by Peter Howard G4UMB, I think, using a hacksaw blade. Now there was hope. Little did I know that this was not going to be a five-minute job. Do you think I had a broken hacksaw blade? Well, eventually I did. Do you think it was straightforward enough to mount the blade in a way that would appear to be feasible to send Morse with? Not the way I built it but, rather than admit defeat, while taking the photo of the key, Fig. 3, I took it apart one more time, looked at my construction under the magnifier and made some more refinements. Now it seemed to converse in dots and dashes.

Before my Mark I Morse key had been refined, Morse key Mark II had taken shape using a microswitch mounted in a plastic box. Was this more successful? Well, it saw action first. I’ll tell you more another time. Next time I’ll share with you some more of the challenges on the way to the first QSO and how I overcame them.

 

This article was featured in the October 2018 issue of Practical Wireless