The Alda 103 “A”


Figure 1:  An almost forty year old Alda 103A amateur band transceiver. Click to enlarge.

Posted Dec 30, 2016:

So, the visitor may notice that I have the “A” model of the Alda, and the “A” model of the Ten Tec Omni. The “A” in the Omni model designation represents “analog” – while the “A” in the Alda model designator means that version of the tribander had been built for the 80/40/15 amateur bands instead of the 80/40/20 bands (original model). AFAIK – the “A” represents a slightly later version of the Alda, so it may incorporate some small improvements in the circuit design.

The Alda 103 has a very interesting history. It was manufactured (IIRC) in 1977 and 1978, which means it has a nice complement of the discrete bipolar transistors that are fairly common (now, almost 40 years later) – and thus replaceable. Readers of some of my other articles may have observed that I like to have the ability to fix the older radios with small, inexpensive discrete components – as opposed to trying to fix more modern radios full of specialty ASIC chips that are eventually available nowhere at any price.  As a bonus, the older radios can often be purchased for a smile and some change.  OK – that’s a situation that’s changing with the emergence of the Ebay industrial level seller, but bargains can still be had.


Figure 2:  Another picture of the Alda radio. Click to enlarge.

According to the lore, ALD Industries was a defense/military supplier of RF decks.  Its owner decided that he needed a better, less clunky, less volumnous radio to take on a sailing yacht cruise around the world.  He used ALD Industries to build the radio, and branded it ALDA (ALD Amateur). Then, for two years, starting in 1977, he made the radio available for hams at large, and at a pretty attractive price too!

Does a defense contractor build a nice radio?  My observation is definitely a “yes”!  For those who are unfamiliar with recreational sailing yachts – they’re a bit like a large motorhome on the water.  So, space is always at a very serious premium.  The Alda 103 scores a direct hit on that requirement.  It’s about the size of two cigar boxes, side by side.  The photo makes it seem larger, because it’s in the foreground.  In reality, it’s barely half the size of the Omni sitting behind it.

Before I purchased my Alda, I made sure that I could source every single solid state device in the box.   Some of those devices were cheaply found in bulk or from NOS internet electronics suppliers (I purchased a hundred of one particular transistor for 6 cents each).  Other parts are more expensive.  The MRF454 final PA output transistors are about $80 for a matched pair.

That brings up a point.  The Omni uses the MRF458 NPN RF power transistor, which is the MRF454’s little brother.  Thus, the diminutive Alda 103 puts out fifty percent more power than the Omni.  The driver for the PA is an SD1285.  Those are still available here and there for about $40 – but I have read that the HF12-20 is a drop-in replacement at ~$20.  I’ll have one on hand just in case I need it.  The driver supplies about 10 watts to the PA.

I have a fondness for these small-form-factor discrete linear technology radios – but am a CW operator for the most part.  Unfortunately, many of the radios in this category are not CW performers.  The Alda’s semi-break-in QSK is smooth and requires no manual switching (unlike some of the Swans).  The audio is very full sounding on CW, and it bests the Omni for SSB audio IMO.

An outboard audio filter could be added, but I’m getting along fine with just the RIT.

The oscillator in the Alda runs all the time, and only the buffer is keyed.  Thus, the note might be expected to be excellent on CW. For some reason, my unit has a little alley-oop in its CW tone on fifteen meters, but on the eighty meter band it’s excellent. That’ll need to be rectified before I power up the Alda within the CW portion of the high band.  The output PA uses the “current method” to limit potential damages during high SWR conditions.  This is something that is better than the situation with the Omni, which (IIRC) relies on a circuit breaker in the power supply to do this task.  My unit had a little bit of a ding on the output, so the SWR protection must not be completely foolproof.

For the curious, I’ve created a short video of the Alda 103A, where I tune around in the CW section of the 40 meter band. I put it on youtube:

Alda 103A tranceiver tour

Internally, the thing is beautiful.  I’ll be adding pics shortly.  As can be imagined, the Alda is chock full of circuit boards due to its two-cigar-box dimensions.  It uses the edge connector plugin board technique, like the slide-in board heathkit transceiver (104 maybe? – and the love/hate relationship its owners had with it).  The Alda has silvered connectors on both sides of the connection (there’s no plain copper).   I’ve not heard any horror stories about the connectors, but then again there are almost no stories at all due to the low number of units built.  Cosmetically, this unit is maybe 9/10 level.  Definitely a keeper!

Read more of my ramblings about the Alda on CW

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