Radios with fixed, pre-set frequencies (Walter Dittel FSG16). Why?

I am in possession of a Walter Dittel FSG16 and I sometimes fly club owned gliders which also carry the FSG16.
To my absolute surprise I found out after several years of using them that they only support 12 pre-selected channels/frequencies which can apparently only be set by an authorized technician (who needs to open the units to set the frequencies). This was a what-the-hell moment.

The first surprise is that I didn't notice this before but that's because I've only been flying "around the patch" where only one frequency has been required and I've never bothered to change it.

The second and bigger surprise is that someone would design and manufacture such a "hard coded" solution.
This seriously limits where I can fly and land as some of the nearby airspace and airports are not in the list of 12 preselect channels. I could get the pre-set channels updated but then if I travel with the glider I'm back in the same situation. I guess a modern unit is in order even though these old units are solid and reliable.

Does someone maybe know why these radios where designed to operate this way considering that communication radios have been tunable in flight ever since they were invented?
Was it to save costs? If so how does it save costs considering that there must be 12 discrete, partial tuning circuits (even if it's just inductors being tuned).
Or was it maybe for a legal requirement in order to restrict glider clubs or owners from selecting frequencies they're not supposed to use?

Scratches and shakes head ...

The FSG16 is an almost 40 years old design. At the time, the channels/frequencies were stabilized with one dedicated quartz per frequency, and the FSG16 was designed to hold 12 quartzes. Simple as that.

On Monday, 8 February 2016 15:29:53 UTC+2, Tango Whisky wrote:
The FSG16 is an almost 40 years old design. At the time, the channels/frequencies were stabilized with one dedicated quartz per frequency, and the FSG16 was designed to hold 12 quartzes. Simple as that.

So 12 individual crystals was a cheaper solution than being able to tune into any of the 720 usable channels that the rest of the receiver unit is capable of?

On Monday, February 8, 2016 at 8:43:46 AM UTC-5, Surge wrote:
On Monday, 8 February 2016 15:29:53 UTC+2, Tango Whisky wrote:
The FSG16 is an almost 40 years old design. At the time, the channels/frequencies were stabilized with one dedicated quartz per frequency, and the FSG16 was designed to hold 12 quartzes. Simple as that.

So 12 individual crystals was a cheaper solution than being able to tune into any of the 720 usable channels that the rest of the receiver unit is capable of?

Correct, same for many radios (including RC radio's). The hardware could cover a wide range, but it was the crystals that did the actual tuning.
Later radios did all this without "crystals" and could also do smaller steps in between freq's.

It's basically the same sort of question as to why did my first tv only have 4 preset channels?
Why was it black and white?

Tech has developed a long way in 40 years.

If you are looking to upgrade just a little, I can offer you a Dittel FSG40s. Just removed from my Libelle, and I am guessing it was new with the ship.

A few years ago the radio in my ASW20 had problems. I took it out and took it apart.

It had the ability to store four frequencies in it (which you could set). To do this it had a couple of large chips which turned out to be memory. Each chip's capacity was 32 bits. Not Megabits. Not Kilobits. Bits.

State of the art at the time, I suspect.

When I was a lad....

So 12 individual crystals was a cheaper solution than being able to tune into any of the 720 usable channels that the rest of the receiver unit is capable of?

No, not cheaper. It just wasn't invented yet. The old radios were all analog. Today they are mostly digital. They use just one quartz crystal and they mathematically change that one frequency to any number you need. These are called "frequency synthesisized" radios. Yes, they are way cheaper than all those custom cut crystals.

How does the FSG16 compare to the other late 1970s electronics you use?

Coincidentally, there's another thread offering a more modern Dittel radio for about $200. The FSG71M is a good radio, but due to the new European regulations a lot of them are available.
Jim

Thanks for the replies and info.
I am aware of the used 25KHz Becker, Dittel and Filser units available in Europe at present so maybe I'll go that route.

On Wednesday, February 10, 2016 at 10:25:38 PM UTC-8, Surge wrote:
Thanks for the replies and info.
I am aware of the used 25KHz Becker, Dittel and Filser units available in Europe at present so maybe I'll go that route.

Surge,

Your old radio is no longer legal to use (it doesn't have the required stability and frequency spacing). Transmissions will likely bleed into adjacent channels. It should be replaced with a 720 channel radio.

Tom