Old ADF
 

Wondering if I can get some help here!
A Cessna aircraft I'm now flying has a very old ADF (1969) - it's one with a big dial in the middle. I've seen one in a PA-28 too.

Being used to a "normal" ADF with a digital output I'm a little perplexed by this device and wondering if anyone knows how to translate frequencies in the chart onto the ADF? It seems to have various subscales and a selector for decimal point position.

Twiddle them till you figure it out?

A picture might help, but generally speaking - the old ones I have flown have a single knob per digit (hence 3 knobs below each digit). When you turn them you should see one of the 3 digits change, and hence get your frequency dialled in.

Sorry if this is a little vague!

These old ADFs are very easy to use.

1. Cover it up with a suitable sized piece of card saying "INOP" in large friendly letters.
2. Use something invented since WW2 for navigation - an iPad works very well.

hahaha best thing I've read in a while!!!

Not sure about what you described. Is it an analog tuner? If so, from memory:

Controls/switches:

* Just like a digitally tuned ADF, it will have a selector, or a couple of selectors, for OFF, ANT, ADF, and BFO.
* It will also have a band/frequency range selector. Use it to tune what frequency range on the analogue scale you wish to tune.
* Frequency scale
* A signal strength meter.
* A tuning knob

To tune a station:

1. Determine the frequency you wish to receive
2. Select the frequency range selector to cover the particular frequency you wish to receive
3. Switch to ANT
4. Select ADF audio 'on' on the aircraft's audio panel
5. Rotate the tuning knob until the needle on the frequency scale is close to the frequency you want.
6. Slowly turn the tuning knob so that the needle continues to move towards the desired frequency.
7. Watch the signal strength meter until it peaks. You may have to slowly rotate the tuning knob back & forth to be satisfied you have the best signal.
8. Listen to the morse ident to confirm the correct station. If it's not correct then you've tuned the wrong station. Check each of the steps above. If you can't hear anything, and are tuning a French NDB, select BFO to add sound to the signal.
9. Select 'ADF' to activate the DF function.

OK Tinny, now see if anyone knows what the BFO function means and/or does.

CC

I miss the one I used to use. It came with a massive aerial running from the tip of the fin to above the cockpit, and made me feel like I was in a DC3. Plus it had excellent gain - it dated from when ADFs were new and exciting.

The digital one may be half the size and a tenth of the weight but somehow it's a bit anodyne.

PS if in doubt, post a photo and we can probably help!

Is it an old Bendix T12?

http://www.hasselbusch-esbeck.de/df2...e/bendix_a.jpg

They are very easy to use.

I used to use one of those in an old Piper twin on the night mail run - it was absolutely fantastic!


For listening to Atlantic 252 :ok:

They don't make em like this anymore.

1. Select the frequency band you need on the right
2. turn the middle knob until you have the approximate frequency shown on the dial
3. fine tune for maximum strength on the left hand meter
4. listen and identify the morsecode.

BFO- Beat frequency oscillator. Not required in the UK but I am told it was required to ident NDB's in France.

Am I correct?

Correct..............

CC

The big plus with these tuneable receivers is that if you're getting interference, you can very slightly de-tune to improve reception - the signal strength meter might be picking up interference. Harks back to the days of trying to tune in Radio Luxemburg - '208, your station of the stars!' Maybe you'll be able to get the Light Programme, or if you're a serious wireless listener, the Home Service. We still get that, locally, on 756 kHz, very handy for practice holds.
If you have such an ADF and it still works, then I'd hang on to it, for as long as there are NDBs about, of course, which might be quite some time.

TOO

BFO is required to hear any A1 signal as it has no modulation and therefore no tone, unless it has something to beat against.
There is no ADF in the World with a digital output! It may have a numeric display, but so does the tuneable one where 300 = 300 and 11 = 1100. Don't people learn to use rulers any more?

Jay Sata - Yes it is!!

Tinny - thanks for the guide. I'm trying to understand how the three scales shown on the dial actually relate to the frequencies displayed on a map - would you have any idea?

That's as maybe but some of use grew up after slide rules and analogue radios and consequently have no idea how on earth these old bits of kit work!

Next to the red 'test' button, is that the volume control knob?

And where is the BFO selector? Is it the CW position?

I have used one of these, I think it was in an Aztec in about 1978.

The one in Jay's picture is tuned to 258kHz. The selector switch on the right selects which range of frequencies is tuned and you rotate the dial referring to the appropriate scale to a position that equates to the frequency you want. All NDBs are low frequency around the bottom of the medium wave broadcast band so their frequencies are in a few hundreds of kHz.
Just to make it a bit more fun, the scale might be inaccurate by a few kHz, which is why you need the Morse identifier to confirm you are tuned to the right beacon.

Most NDBs are amplitude modulated with a tone so you don't need a bfo. Bfo would be needed to hear the tone (so you can read the Morse) if it is carrier wave only (A1 modulation: that means the Morse is sent by turning the signal itself, or 'carrier wave' on and off.

1940's technology but good stuff nonetheless.

I agree with you Heston. I was based near the Bristol Channel decades ago and could navigate direct back from France using the 75 killowatt BBC Wales transmitter at Washford. I could pick it up on the ground at Schipol.

They were wonderfull bits of kit in Australia where a MW radio station could be used as a homing beacon and provide in cockpit entertainment.