Beacons for The Rock NSW

[VK2KRR]

Is there anyone or group out there who would be prepared to knock up a number of beacons that I could run up here?? I only really need the transmitters/morse generators. Im not sure how they work, I have had nothing to do with them.

I wouldn't mind running 2-70-23 and maybe a 10 GHz beacon or anything else in between.

I should be able to supply power supplies, cables and antennas, I also have a spare tower. I'd like it to run on batteries with a solar charger if possible.

The beacons could be on permanent loan for as long as its operational perhaps, if anyone has spare bits and the know how. Im not sure whats required, but I do have some FM92 rigs here for the VHF band if they could be of use.

Im sure the beacons would be a handy thing to have here for people abroad to listen for as its a pretty unique area here for tropo.

[VK2OMD]

Is there anyone or group out there who would be prepared to knock up a number of beacons that I could run up here?? I only really need the transmitters/morse generators. Im not sure how they work, I have had nothing to do with them.

I wouldn't mind running 2-70-23 and maybe a 10 GHz beacon or anything else in between.

...

Leigh, are you taking account of the noise that transmitters produce? It is likely that a co-located beacon transmitter would prevent weak signal operations on the same band due to the noise from the beacon transmitter.

Perhaps an experiment with a 144 or 432 FM transmitter running 10W might give you a feeling for the noise to expect.

To be useful, a 10GHz beacon probably needs to be GPS locked... otherwise finding its current frequency becomes too great a variable. Would you propose a directional antenna? Microwave paths basically depend on huge gain at BOTH tx and rx to allow the use of relatively low power... and at 10GHz, a high gain tx antenna basically means a dish.



If you are satisfied that a transmitter will not degrade your own operations, I previously posted an article here on a keyer that might be of interest: http://www.expandedspectrumsystems.com/prod5.html . VK1BL and I each have one of these (the FB1) and they are excellent... if you don't have an existing method of making a Morse beacon in your shack (eg a Morse keyboard), then one of these should be in your toolkit. Ted used one of these for lining up our several 10GHz contact paths on our recent field trip to Mt Gray (Goulburn) and Mt GIbralter (Bowral) where we explored contacts with Sydney and Canberra. The pic above is my FB1 built in a UB5 Jiffy Box.

Owen

[VK4VU]

Gents,

I agree that strategically located beacons can be a great asset, particularly with the sparse distribution VHF/UHF stations in this country.

My view is similar to that of Owen's, in that you would need to be careful colocating a beacon transmitter with a weak-signal receive system.

Owen's comments about the in-band phase noise from the beacon transmitter are very valid. The other contributing factor is the phase noise of you own equipment, which, in the presence of strong local signals will manifest itself as an elevated noise floor in your receiver. This is known as reciprocal mixing

http://www.radiolab.com.au/DesignFile/PNRef/rx1.htm

The other issue might also be straight receiver blocking.

Many of the modern VHF/UHF transceivers are famously (in-famously ?) deficient in both respects, as reported by DF9IC in his comprehensive report.

http://www.df9ic.de/tech/trxtest/trxtest.html


Hope this helps.

73

Rod Preston VK4KZR

[VK2ZRH]

Hi Leigh,

Owen VK1OD rightly mentions the issue of phase noise from a co-located transmitter.

However, this can be addressed in the design of the oscillator to derive the beacon's carrier frequency.

A short exposition on the issues, Oscillator design for low phase noise, is on the Radio-Electronics website here: http://www.radio-electronics.com/info/r ... llator.php

Then you might cast your eyeballs over the Analog Devices application note, A Discrete, Low Phase Noise, 125 MHz Crystal Oscillator, on their website here: http://www2.analog.com/static/imported- ... 7an419.pdf

The circuit used in this app. note is the Butler oscillator, application of which is covered in Survey of Crystal Oscillators, by yours truly, published in Ham Radio, March, 1976, pp 10-22, available online here: http://www.pan-tex.net/usr/r/receivers/ ... scref2.htm

And if you really want to dig deep into the subject, try this paper: Oscillator Phase Noise: A Tutorial, by Lee and Hajimiri, 2000, IEEE Journal of Solid State Circuits, Vol. 35 No. 3, March. Get the PDF here: http://www.chic.caltech.edu/Publication ... _tutor.pdf

Hope at least some of that helps.

73, Roger Harrison VK2ZRH

[VK2OMD]

Hi Leigh,

Owen VK1OD rightly mentions the issue of phase noise from a co-located transmitter.

...

My comments were not restricted to phase noise, nor were they intended to be.

A transmitter PA stage, its drivers etc all produce noise that is fed to the antenna irrespective of whether there is a 'signal' in the path. Key an SSB tx up with no modulation, and there is substantial noise (in the weak signal context).

Of course, in band signals can intermodulate in the tx path and make more noise.

Additionally, multiple transmitters will intermodulate in each other's output stages and make noise. Filters are used on sites with multiple transmitters to keep one tx output out of another's PA to try to reduce this source of noise.

All this is without visiting the imperfections in your own receiver, as Rod mentioned, the existence of nearby very strong signals generates more noise.

I am not saying it cannot be done, just flagging that these are issues that should be considered in a site design context, and some basic experiments will reveal the potential.

Owen

BTW, I use the term noise to mean undesired signals, and not to imply Gaussian noise.

[VK2KRR]

Just to further clarify. If they were on my property I would like to be able to turn them off when Im on air. As you dont need beacons when im on air, I am the beacon
But as I am not on air currently as much as usual and off doing other things (which should have been done ages ago) I thought it would be handy for other people to have something to look for up here when I am not active.
I do know a few other property owners where they could go, but thats probably not ideal as I would be beaming at them and mainenance is not as easy. Here I could have them up the back of the property, much higher than the house. But then again, height is not might with tropo at times.

What I would envisage for 2m for example, is possibly a power divided output set up as there is no point having RF going east or north from here due to the massive hill. Main points of interest are Melbourne, Mt Gambier, Adelaide. 3 broad beam widths in those directions would be ideal and should be enough to cover points in between sufficiently anyway. 3 or 4 element yagis should do. Realistically there is not a great deal of interest north of the Mildura direction.

I guess on 10GHz it could get tricky, Ive never operated at 10 GHz, if it was possible to at least divide into 2 small dishes that would be handy. Another idea could be a single dish and I could alternate locations. At this stage Ive only had interest from Melbourne/Geelong in 10GHz so possibly locked Melb direction unless others show interest.

Maybe as a starter, I could look at getting something on 2m running and if that works out we can look at other bands ? Maybe its not worth it at all ?? But I am making an offer to try something.
Like I said, I really need the transmitter unit/morse generator ready to be plugged into power and antenna.

[VK2ZRH]

Mea culpa ! You're right, Owen. Perhaps I should have assigned raising the 'phase noise' issue to Rod VK4KZR.

Indeed, there are a number of noise sources to consider with co-located transmitters . . . and enough references for Leigh to while away a few evenings.

Moving right along - Leigh, if you're considering running the beacon/s ". . . on batteries with a solar charger . . .", then you might like to consider having the RF power stages run Class-E or Class-F, which yield high efficiency (along with other advantages), taher than Class C.

The seminal paper on Class-E RF power amps, Class E - A New Single-Ended Class of High-Efficiency Tuned Switching Power Amplifiers, by Nathan and Alan Sokal (both amateurs), published in the IEEE Journal of Solid-State Circuits, June 1975, is available online here:http://www.physics.princeton.edu/~mcdon ... 168_75.pdf

A 2001 article in the ARRL's QEX magazine for Jan/Feb 2001, by Nathan Sokal (WA1HQC), Class-E RF Power Amplifiers, is on the ARRL website here: http://www.arrl.org/tis/info/pdf/010102qex009.pdf

A tutorial on the subject, by the same author - Class-E high-efficiency RF/microwave power amplifiers: principles of operation, design procedures, and experimental verification - can be downloaded here: http://www.cs.berkeley.edu/~culler/AIIT ... eramps.pdf

A practical implementation of a 20 W 145 MHz Class-E transmitter for satellite use is described by Franco and Katz, Class-E Silicon Carbide VHF Power Amplifier, is here for the taking: http://www.cree.com/products/pdf/Class- ... lifier.pdf

For a comprehensive dissertation on Class-F (Class-E on mild steroids) RF power amps, you can't go past Investigation of Inverse Class-F Power Amplifier for High Efficiency Operation by Amy Van Munn, online at: http://www.ece.ucsb.edu/rad/pubs/master ... n_2004.pdf

More reading to while away evenings in the country.

Posted in the interests of advancing the art of beacon design and deployment.

73, Roger Harrison VK2ZRH

[VK2KRR]

There is no point telling me, tell the beacon guru people. I already know about noise floors and power issues.
So far there has only been one person capeable of putting a transmitter together contact me and it was not from the VK logger post.

Is there anyone or group out there who would be prepared to knock up a number of beacons that I could run up here?? I only really need the transmitters/morse generators.

Pretty simple question really...

[VK4GHZ]

Six meters has it's fair share of personal beacons.
To cut a long story short, they're pretty much a waste of time from everybody's perspective, everybody except the person who runs it.

Why?
Because everybody else can have no confidence in whether it is actually running, or not.
Being turned off at the whim of the operator cannot be predicted... so it can be waste of time listening for it.
It could well be posted on a Logger that the "beacon is running now", but not everybody watches Loggers, let alone have internet capability.

You would be better off installing a permanent 24/7 beacon in an appropriate location (appropriate to both you, and the intended audience).
Then it can be trusted to be running, and then becomes worthwhile for others to listen out for it/them.

Otherwise, you could save yourself a lot of hassle with extra TXs, and put your own rigs into "beacon mode" with keyers.
At the end of the day it's the same thing - you are turning the keyer off when you want to listen.

My 3 cents.

[VK5PJ]

At one stage I thought that running a beacon from here on 144.455 while the Adelaide beacons were off was a good idea but as Adam rightly points out, no one will look for it if its only on when the person remembers to turn it on. Plus while it was going here at home from the lower shed it raised the noise floor of two metres terribly.. I could still operate but the signals had to be strong.

I had it going for several months over the summer period before the Adelaide beacons returned, advertised it on the logger but received zero reports on its operation (10 watts into a 5 element yagi pointed out along the vk3 / vk2 border country).

Why?
Because everybody else can have no confidence in whether it is actually running, or not.
Being turned off at the whim of the operator cannot be predicted... so it can be waste of time listening for it.
It could well be posted on a Logger that the "beacon is running now", but not everybody watches Loggers, let alone have internet capability.

You would be better off installing a permanent 24/7 beacon in an appropriate location (appropriate to both you, and the intended audience).
Then it can be trusted to be running, and then becomes worthwhile for others to listen out for it/them.

A beacon run on a whim is pretty well counter productive, if its on, you know there is no hope of a contact. If its off.... well either you forgot to turn it on, you are on the band some where and just can not work out where or maybe there is no propogation at all. this does not enspire one to come back and look for it more than a few times before you become dis-heartened.

Leigh save your self the time and energy, either make the beacons 24 by 7 and predictable or leave it alone.... I for one after my experiences with personal beacons would not even bother looking for a beacon that might or might not be there... there is more fun to be had watching paint dry or trying to predict how many KHz the Mildura 144 MHz beacon has drifted down the band by today.

Sure enough if you have a special arrangement with a distant station to look for a boutique beacon at certain times, go for it but you can not expect the main stream VHF people to be looking for them on an adhoc basis.

[VK1XX]

Leigh
I have heaps of beacons, all standalone with keyer, 'cavity' filters etc etc

but there is no way mate in hell that you want to run it at your own house...take it from me.....

unless you can get 100 to 300m separation from it, and put it in a direction you never want to beam.....

I have the VK2CCW beacon on at my place 24h. I have 2 x 6" quarterwave bandpass filters on the TX and 26" quarterwave notch filters on my 2m RX, for FM, 2MHz away.

Now, if you have 300m in hand, then that's no real problem... or at least 100, minimum. Then, with a single filter on a 2m beacon, that will prrobably be OK.
It will possibily cause your receiver IM in the city, but out there under the rock should be OK.

What do you have ????

Glen

[VK2KRR]

Hi Glen

I could probably get 300m away from the required direction. But I was not planning on running it while on air anyway. And thought it would be handy to make use of my location as a beacon when the rigs are not on etc.
There is not enough interested people to make it worth while I dont believe, so I wouldn't worry about it any longer. But thanks for the offer in any case will keep it in mind.

[VK1XX]

300m spacing is ok, but they've got to be 24/7 with a good power supply, and mains, unless you want to fork out for say a 200W of solar panel to support a 10W beacon.

Part time beacons are an annoyance rather than good thing.

cheers

[VK4GHZ]

Part time beacons are an annoyance rather than good thing.

Hear, hear.

Operators rarely listen out for part time beacons, because there is zero confidence it is actually running at that point in time.
Either run the beacons 24/7, or not at all.

Actually, when I say 24/7, you can assume there is little point running them through the dead of night, considering the frequencies of interest.
HF would be different, of course.
In this case, a mains timer will save operating costs, and you might activate the system from, say, 20:00 - 12:00 UTC everyday.