434 Wave Propagation

[Beaner]

This thread is predominantly aimed at Robert but I would be interested in anyone's opinion on 433 transmitter wave propagation.
I must state for the record that I do run 434 and I am very happy with the equipment, signal bounce did have me scratching my head a little but that is all part and parcel of learning to use a new system.
The most often heard comment I get when discussing telemetry with my fellow falconers is the 433/ 434 is great for line of sight but if you are using in hilly and wooded areas (where I hunt) a lower frequency is much better, I myself have never had a problem tracking down my hawk in such landscape.
I understand the whole signal bendy thing reasonably well but would be interested in knowing how Marshall have managed to get the system to work outside it's theoretical norm, for example in one of my track downs I found my hawk tight up against the base of a 12ft river bank and I was 3/4 of a mile away on the blindside.
Was this just signal bounce, the extra power output, a combination of the two or just pure luck that saved the day?

[rkumetz]

This thread is predominantly aimed at Robert but I would be interested in anyone's opinion on 433 transmitter wave propagation.
I must state for the record that I do run 434 and I am very happy with the equipment, signal bounce did have me scratching my head a little but that is all part and parcel of learning to use a new system.
The most often heard comment I get when discussing telemetry with my fellow falconers is the 433/ 434 is great for line of sight but if you are using in hilly and wooded areas (where I hunt) a lower frequency is much better, I myself have never had a problem tracking down my hawk in such landscape.
I understand the whole signal bendy thing reasonably well but would be interested in knowing how Marshall have managed to get the system to work outside it's theoretical norm, for example in one of my track downs I found my hawk tight up against the base of a 12ft river bank and I was 3/4 of a mile away on the blindside.
Was this just signal bounce, the extra power output, a combination of the two or just pure luck that saved the day?

The "signal bendy" thing as you call it is a somewhat complex issue. Obstructions vary from rolling hills to a knife edge and everything in between. All will be different in terms of how signals bend over them.
Based on shape and what the obstruction is physically composed of.
Another factor is that sometimes when you have a signal down behind an
obstruction you may get a reflection off of something further away than the obstruction that separates you from your bird.

Beyond that you need to consider a few other factors. The UHF transmitters have higher output power than the 216 ones which makes up a bit for other places where 216 looks better on paper. The antenna on a UHF transmitter is usually full length rather than an electrically shortened version so the antenna is more efficient as well. A full quarter wave on UHF is about 6.5" while at 216 it would need to be 13".

There are also other odd factors that may come into play. For example higher frequency signals tend to penetrate reinforced concrete better than lower frequency ones because the spaces between the rebar are large enough to not offer as much shielding. This same type of behavior may come into play with other types of "shielding" such as foliage, etc in some cases even though the absorption is generally higher at UHF.

I have been in radio related fields for over 35 years and the most important thing that I have learned is that radio is not entirely a science.
It is part black magic. Sometimes radio signals behave in ways that are not explainable by the books and leave you scratching your head. That is where experimenting with the equipment before you need to track a bird will pay off.

[calebstroh]

Great last paragraph Ron (not that the other stuff wasn't! )

I'm relatively new to all this stuff so take this for what its worth. I believe readying the signals and comprehending the radio physics is only half the picture (the "on paper" aspect.)

While simple things, as have been mentioned, like learning the nuances of "your" receiver, knowing where the birds "aught-to-have-flown-to", getting there fast...and for gods sake: TRIANGULATE! Such thinking and methods is often as much help as the "device" itself lends to the situation.

Anywho, I had the pleasure for helping a great friend try and recover a lost wild-taken Anatum falcon...boy was that fun (for me) not so much for him. Good story though and the bird was trapped like a pure wild Peregrine with a dho-gazza. It was "On Hack" for better than a week and none-too-keen on coming home!

Used religiously, common cents often saves the day.

[Beaner]

Thanks for the replies and yes you are both correct you need to get to know your system before you need to use it in anger but what I am trying to convey is that the Marshall user guide only really touches on the basics of telemetry tracking and some additional information on how 433/ 434 works would be of a great help during the initial learning curve and help reduce the stress levels a little when your hawk does decide to do one.
With regard to the "signal bendy thing" which is just my friendly name for signal diffraction, multipath is also an influencing factor and so are a few others already mentioned.
I don't profess to be an expert by any means but it did take me a little while to work it all out in my head before I was happy I understood the basics.
The main issue for me was multipath signal bounce which is basically when you do a 360 degree turnaround instead of getting 1 or 2 (primary and 180 degree reflected, which I was used to on my old system) indications you end up getting 3,4 or more, what works for me if I do get multiple signals is turning down the volume down to reduce the gain to 2 or 3 on the dial to find the strongest signal through finding the signal drop off edges and dividing in half to get an initial bearing (note unsurprisingly the iPhone has an app for that!!) move position and repeat this will give you an idea of where your bird is if say she is on a kill.
Large very dense cover can also be a bit challenging to pinpoint a bird when she is on a kill as invariably the crafty little so and so will not give the game away with a jingle of its bells and the high power of the transmitter can confuse matters, at this point I wish my hawk had been born florescent orange just to make my life a little easier but I have in the past shifted slightly off frequency on my receiver by .001 or .002 just to further reduce the sensitivity and get you to within a couple of feet or so. Not tried it but I have been told the the signal sensor can also be used for pinpointing a transmitter, say if it had been dropped in a field or wood.
What I will say is if you have a signal you can be 99.9% confident you will find your bird and that if your bird is like mine and misses her mark she will typically come back and find me so don't be in any rush move position immediately just get your receiver out and have a scan.

For me its all about allowing the hawk to fly and not trying to micromanage it and today's telemetry helps me do just that.

[forensics]

I will switch back and forth from external to built in and as well adjust signal sensor to ascertain better location. My largest obstruction is also hills/valleys and trees. That's where switching back and forth on antennae and then adjust sensor to better fine tune. Practice makes perfect. I ran many dry runs to figure mine out.