What voltage is best to run a traffic light horn at (AGD) I'm having trouble linking at 7.2v.

It's sounds crazy but Iv actually run these at 19v before and it was almost as easy as band 1. But Iv heard they put out bad signals past a certain voltage.

Anyone got any idea ?

As I remember, 6 - 8V is about right for these. Some people complained about poor bass response with these, but it was just that every idiot rig builder used a copy of a deliberately erroneous circuit diagram with the mod feed capacitor 100 times too small! This incorrect information was circulated to demonstrate that the worthless idiots copying my designs, or Roger's designs really didn't have a clue. If they knew anything at all about electronics, they would have spotted the deliberate error immediately. They didn't even know enough to try paralleling an extra capacitor to see if it improved things!
The AGD module got a bad reputation for poor audio, leaving endless unwanted horns for those of us who knew better!

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Yeh iv never had any problems with agd. I used a test satcan and changed between the agd and a large c&k and I couldn't hear any difference in bass or treble.

7.1v to 7.5v at horn if u have a long cable check at horn end

Agd with the Allen key type tuning screw sound a lot nicer at around 5.5v, they don't drift at this voltage and link solid. Any other gunn is around 7-7.5v ish for best sound quality.

Albert H wrote: ↑Tue May 02, 2017 5:56 pm As I remember, 6 - 8V is about right for these. Some people complained about poor bass response with these, but it was just that every idiot rig builder used a copy of a deliberately erroneous circuit diagram with the mod feed capacitor 100 times too small! This incorrect information was circulated to demonstrate that the worthless idiots copying my designs, or Roger's designs really didn't have a clue. If they knew anything at all about electronics, they would have spotted the deliberate error immediately. They didn't even know enough to try paralleling an extra capacitor to see if it improved things!
The AGD module got a bad reputation for poor audio, leaving endless unwanted horns for those of us who knew better!

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The agd with ordinary flat type tuning screw (from the grey casing) were heavily surpressed and would not modulate fm very well, they distorted when very lightly Modulated. They were not useable. I think you must be referring to a different horn. I worked at Siemens for a short while and had access to loads of these. They was even pulled from production as they was failing out on the road. They then introduced the black body detectors which contained the Allen key tuning screw, these are by far the best horns I've ever used.

Over the years, I've used lots of different microwave gear. The big Gunn head with two diodes that was used in some AGD traffic gear was superb! The first thing I did when I got some of these was to set up a PLL system (look in the ARRL Microwave handbook for tips on how to do this). The frequency stayed exactly the same whatever the temperature. The output power was decent, too. I had one of these linked to a cheap LNB and a PLL receiver over a 42km path!

Just out of interest, what sort of distance have you got using these type of horns? Do the get issues due to weather or anything?

The most I've done at a guess is about 15miles from a big hill in my area. We linked from a car battery and used the 'Allen key' agd gunn, I had to use a sky mini dish and satellite finder at receiving end to position it. I'm sure it would go further, it was too weak and inaudible without the dish, even with the dish it wasn't that great

I've just googled the path I linked and it's exactly 16.6 miles, very disappointing compared to alberts 42km

I only use these around 1-2 miles away lol and still have Drift issues sometimes.

OldskoolPirate wrote: ↑Fri May 05, 2017 1:24 pm I only use these around 1-2 miles away lol and still have Drift issues sometimes.

Unfortunately Gunns are prone to drifting with temperature change.
A neat and cheap little way of fixing this is using a CCTV camera housing, they are around £15 - £20, you want one with built in heater and thermostat. This will maintain the temperature in the housing, however this wont help if the sun is glazing down on it so try to keep it under cover
Housing similar to this on ebay but with an added heater 222156062049

You could easily build a thermostat and use a large resistor as a heater for under a few quid if you already have your horn in a housing

I've used temperature stabilisation, too. My favourite method is to use a chunky power transistor, a metal-clad power resistor and a simple regulation circuit based around a slow op-amp. I use a small plastic-bodied NPN transistor as the temperature sensor. The whole horn is taken up to about 45C, and kept there (to within about 0.5C). If anyone wants the circuit, I'll post it up here.