2m Sprint-TX test practice

2m Sprint-TX test practice

Today was a lovely sunny spring day here in Melbourne, a perfect opportunity to test the new set of 2m Sprint transmitters, following a Street orienteering (Cake-O) event in the far eastern suburb of Chirnside Park. This was also a brand new map, the first time a street-O has been run in Chirnside. The Start/Finish location was the beautiful and manicured Delemere Reserve.

A number of ARDF regulars decided to make the trek to dabble in a bit of Sprint practice, as well as most also competing in the orienteering event prior (which wasn’t quite as hilly as I’d expected beforehand).

The results for the Sprint TX testing appears below too.

---

Rough Results

Competitors self-timed, as this was only an informal practice, but for the heck, here are the recorded results. You’ll note for both Jack and Jenelle I’ve only awarded 4 TXs. Perhaps Jenelle forgot to get TX#3 ? There’s no punch there anyway. In Jack’s case, he has the wrong punch mark for TX#5. Now I don’t know quite how he managed this, as there was only one punch at each TX. I can only assume he has punched at some random orienteering control, or perhaps at the grey practice FoxOr, instead (in the big tree just near the start) !?!

 

Name	#TXs	Time	Place
Kris Ruuska	5	10:14.00	1
Monica Lo Presti	5	30:30.00	2
Ewen Templeton	5	33:00.00	3
Jack Bramham	4	26:00.00	4
Jenelle Templeton	4	35:00.00	5
Uncle Rod	1+	?	6

 

 

 

---

Testing, Testing…

Another reason was to test the new sprint transmitters in the field for the first time.

Successes:

• They all turned on at 2:30pm that afternoon, as programmed to 2 days before, and the transmit sequence was perfect, with no overlap between transmitters.
• Battery voltage tests afterwards show all transmitter batteries had barely discharged at all, after running for a couple of hours (and 2 days sleeping). Even the Homing Beacon, which has the highest duty cycle, the LiIon cell was still above 4V. Lowest was 3.77V on the test FoxOr transmitter.

Room for improvement:

• Some had difficulty DFing and IDing the transmitters at the same time. This may be because the CW is achieved by turning the final off and on, but the exciter stays on during the whole 12s. This means in practice, in whoopee mode, the sniffers alternate between a high and low tone, rather than being a definite OFF between the CW pulses, and this is harder for the brain to figure out. Another test version of firmware from Byon turns on and off the entire transmitter, but this suffers from a slow PLL re-lock time, making the pulse ‘soft’ and too short (the lock time was nearly as long as a dit). Perhaps a new special version that pre-turns on the PLL before each final stage pulse could help. Alternatively, something kludgey that shorts the exciter output during the OFF might improve things.
• There is currently no modulation on the transmitters. Only FM modulation is available, and this seems to spread the power available over a wider frequency band, reducing the range of the transmitters significantly (liatening on whoopee, the exciter alone produces a higher whoopee tone than the modulated FM with final on, effectively inverting the morse, making it very hard to read!). Jack had problems with the Nick Roethe 2m sniffer, as it only engages whoopee when close-in, and with no modulation not much could be heard on AM. No easy solution to this one.
• Perhaps the dits could be a bit longer. This can be manipulated somewhat in the MicroFox programming, but any changes would then need to be re-cal’d on all transmitters so the on-time window is correct for an integral number of morse words.
• The Homing Beacon seemed to be down on power at the end. The battery was not the cause of this. Needs investigation. Is the PA getting warm ?
• Feedback on anything else ?