[OZAPRS] HF Gateways

Jamie Campbell - VK2YCJ vk2ycj at bravo.net.au
Mon Jun 29 17:48:02 EST 2009


Ray,

Ah, I see.  Very Interesting stuff.

In Internet terms we could say that they are similar to TCP/IP and UDP 
packets.  Most Internet things use TCP/IP as it gives a guarantee of 
delivery.  UDP is used for things like VOIP where time is of the essence and 
packets are sent but not checked to see if they are delivered.  Typically 
TCP/IP will keep on resending to get the data through (within reason).  UDP 
will try once, but there are exceptions where certain applications like 
username and password authentication where the application will send the UDP 
packet 3 times in case it goes missing.  That way you have 3 chances of 
losing the packet.

I suspect that Echolink doesn't use a standard VOIP UDP protocol because I 
have NEVER heard a crook Echolink transmission.  I'm guessing, but because 
it is a simplex transmission with a bit of buffering they can probably use 
TCP/IP to guarantee delivery and the buffering covers up any instability or 
jitter that might affect the quality at the other end.

I'm thinking aloud here ....



Jamie Campbell
vk2ycj at bravo.net.au


You'll never reach your greatest potential if you walk
past the dishwasher without emptying it or leave your
costume on the bathroom floor.

(Nancy-Bird Walton, Australian Aviatrix, 1915-2009)


----- Original Message ----- 
From: "Ray Wells" <vk2tv at exemail.com.au>
To: "Australian APRS Users" <ozaprs at aprs.net.au>
Sent: Monday, June 29, 2009 3:49 PM
Subject: Re: [OZAPRS] HF Gateways


> BBS operation is a little different from APRS in that if a frame isn't 
> received/acknowledged, it's sent again. The UI frames of APRS are launched 
> into the never never with no guarantee of delivery.
>
> BBS operation also has an advantage over two operators trying to have a 
> digital contact because if frames aren't received now, they might be 
> later, possibly hours later. Even the "dead at night" nature of 40m 
> delivers some frames in that "dead" time. It's not unusual to hear the 40m 
> rig forwarding at 1.00am - the shack is in the house and I hear the PTT 
> relay going, and the reply packet.
>
> Ray vk2tv
>
> Jamie Campbell - VK2YCJ wrote:
>> Ray,
>>
>> What an interesting story.  I enjoyed reading it and chuckled on the way 
>> through.  Thanks for the snapshot of your 10 years of packet.  I'm going 
>> to tag this email and come back and read it again so I can absorb it.
>>
>> I guess with APRS the amount of data being sent is quite small compared 
>> to a slow scan image or digital file.  Being small probably gives it an 
>> advantage in getting through particularly with the data packet techniques 
>> you mentioned.
>>
>> Thanks again for the story ...
>>
>>
>> Jamie Campbell
>> vk2ycj at bravo.net.au
>>
>>
>> You'll never reach your greatest potential if you walk
>> past the dishwasher without emptying it or leave your
>> costume on the bathroom floor.
>>
>> (Nancy-Bird Walton, Australian Aviatrix, 1915-2009)
>>
>>
>> ----- Original Message ----- From: "Ray Wells" <vk2tv at exemail.com.au>
>> To: "Australian APRS Users" <ozaprs at aprs.net.au>
>> Sent: Monday, June 29, 2009 2:31 PM
>> Subject: Re: [OZAPRS] HF Gateways
>>
>>
>>> Jamie,
>>>
>>> Each of us who has reported their experiences with 80m are reporting 
>>> just that, their experiences. We all know how Mother Nature can be with 
>>> propagation and experiences that contradict my own don't surprise me.
>>>
>>> What does surprise me are comments that HF packet won't work for this, 
>>> that or another reason. Sometimes those comments are from people who 
>>> haven't actually used it. Sure it has its limitations at times but it 
>>> can be surprisingly good.
>>>
>>> I've been using 0k3 HF for BBS forwarding for over ten years on a 24/7 
>>> basis so I'm probably reasonably well qualified to comment. My initial 
>>> activity was on 30m when I forwarded with a vk3, and later with a vk5. 
>>> Both paths were consistently open 22 hours per day. About seven (maybe 
>>> six) years ago I started using 40m between Kempsey and Sydney (vk2aab), 
>>> with great success. Steve (vk2slm) in Casino joined us maybe two years 
>>> ago. I forwarded with another station in Forbes for a while. Steve and 
>>> Barry are each a similar distance from me, but in opposite directions. 
>>> Propagation over those two paths is quite different.
>>>
>>> The two factors that influence performance the most are static crashes 
>>> and phase distortion. Provided a storm isn't too severe it is still 
>>> possible
>>> to forward data. Phase distortion is something else again. There can be 
>>> S9+ signals but no data gets exchanged. Frustrating to say the least. An 
>>> important factor for HF packet is to keep paclen low. I use paclen 64 
>>> and maxframe 1, those values being arrived at empirically. FRACK also 
>>> needs to be set high to reduce retrying out. I run about 13 seconds. The 
>>> shorter the frame the greater the chance of getting through. And 
>>> maxframe one ensures that multiple packets don't have to be resent in 
>>> the event of one corrupted packet.
>>>
>>> When I first started using HF on 30m I was using Flexnet which, some of 
>>> you may recall, automatically sets parameters such as maxframe and 
>>> frack. The vk3 path was so good that Flexnet would set maxframe to 7. It 
>>> was Flexnet that determined frack should be so long.
>>>
>>> Do you remember why amateurs were originally given HF? It was given 
>>> because governments believed we'd never get out of our own back yards 
>>> with such short wavelengths. We tried and succeeded. Apply that 
>>> philosophy to HF packet.
>>>
>>> Ray vk2tv
>>>
>>>
>>> Jamie Campbell - VK2YCJ wrote:
>>>> Ray,
>>>>
>>>> Good on you for making some positive comments on 80m.  It's a good band 
>>>> during the day for some reasonable coverage.  I get good reliaable 
>>>> coverage on 80m all day (during the daylight hours) - probably 
>>>> 300Km-400Km or so. The Dural morse code beacon near to 3.7 Mhz is 
>>>> generally S9/ +20 to +40db all day.  Newcastle to Sydney and Kiama is 
>>>> dead easy too.  Mid to late morning (9am-10am) often gives good but 
>>>> scratchy coverage Newcastle to Melbourne.
>>>>
>>>> Local noise levels would be a problem for a mobile station though.
>>>>
>>>>
>>>>
>>>> Jamie Campbell
>>>> vk2ycj at bravo.net.au
>>>>
>>>>
>>>> You'll never reach your greatest potential if you walk
>>>> past the dishwasher without emptying it or leave your
>>>> costume on the bathroom floor.
>>>>
>>>> (Nancy-Bird Walton, Australian Aviatrix, 1915-2009)
>>>>
>>>>
>>>> ----- Original Message ----- From: "Ray Wells" <vk2tv at exemail.com.au>
>>>> To: "Australian APRS Users" <ozaprs at aprs.net.au>
>>>> Sent: Monday, June 29, 2009 12:19 PM
>>>> Subject: Re: [OZAPRS] HF Gateways
>>>>
>>>>
>>>>> I wouldn't write off 80m completely, even though its use would be 
>>>>> limited.
>>>>>
>>>>> Yes, the static crashes at night are a downer but if you're looking at 
>>>>> relatively short range - out to about 400km - and you can erect an 
>>>>> antenna, daytime 80m is remarkably good. Mind you, a local daytime 
>>>>> electrical storm has quite an impact too :-(
>>>>>
>>>>> When I did a lot of travelling with HF onboard, if I could erect a 
>>>>> dipole, albeit close to the ground, we regularly (read as daily) 
>>>>> worked out to 400km. Signal levels were often low but there was 
>>>>> usually little band noise so s/n ratio was high. FM was performance 
>>>>> was quite impressive compared with SSB. We did some testing with 
>>>>> narrow deviation.
>>>>>
>>>>> VK2AAB and I came very close to resorting to 80m for daytime BBS 
>>>>> forwarding some months back when 40m (our usual band) completely died 
>>>>> for quite some weeks. We're nearly 400km apart. 40m came good and we 
>>>>> didn't have to try 80m.
>>>>>
>>>>> Ray vk2tv
>>>>>
>>>>> VK2KFJ wrote:
>>>>>>  yeh pretty much the noise & static crashes,   and its useless during 
>>>>>> daytime.
>>>>>> I remember some guys trying packet radio on 80m years ago and they 
>>>>>> gave up that it was easier to pick up the microphone to get a message 
>>>>>> through.
>>>>>>
>>>>>> Steve VK2KFJ
>>>>>>
>>>>>>
>>>>>> --- On Thu, 25/6/09, Jamie Campbell - VK2YCJ <vk2ycj at bravo.net.au> 
>>>>>> wrote:
>>>>>>
>>>>>>
>>>>>>> From: Jamie Campbell - VK2YCJ <vk2ycj at bravo.net.au>
>>>>>>> Subject: Re: [OZAPRS] HF Gateways
>>>>>>> To: "Australian APRS Users" <ozaprs at aprs.net.au>
>>>>>>> Received: Thursday, 25 June, 2009, 10:49 AM
>>>>>>> Steve,
>>>>>>>
>>>>>>> Thanks for the reply.
>>>>>>>
>>>>>>> Would you not bother with 80m because of the noise (mainly
>>>>>>> at night) or the relatively short range during the day ?
>>>>>>>
>>>>>>> Okay, does that mean that 40m is the most popular at
>>>>>>> present ?
>>>>>>>
>>>>>>> 40m isn't too crash hot now with the sunspot cycle the way
>>>>>>> it is, although if there was an abundance of base stations the 
>>>>>>> coverage
>>>>>>> could be extremely good.
>>>>>>>
>>>>>>> With a few dozen $150 boxes around the place we could have
>>>>>>> "armchair coverage" across Australia, haha :)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Jamie Campbell
>>>>>>> vk2ycj at bravo.net.au
>>>>>>>
>>>>>>>
>>>>>>> You'll never reach your greatest potential if you walk
>>>>>>> past the dishwasher without emptying it or leave your
>>>>>>> costume on the bathroom floor.
>>>>>>>
>>>>>>> (Nancy-Bird Walton, Australian Aviatrix, 1915-2009)
>>>>>>>
>>>>>>>
>>>>>>> ----- Original Message ----- From: "VK2KFJ" <vk2kfj at yahoo.com.au>
>>>>>>> To: <Ozaprs at aprs.net.au>;
>>>>>>> "Australian APRS Users" <ozaprs at aprs.net.au>
>>>>>>> Sent: Thursday, June 25, 2009 10:28 AM
>>>>>>> Subject: Re: [OZAPRS] HF Gateways
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Hi Jamie,
>>>>>>>>
>>>>>>>> you just wouldn't bother with 80m,
>>>>>>>>
>>>>>>>> however, you on the right track at looking at cheap
>>>>>>>>
>>>>>>> dedicated xcvr,
>>>>>>>
>>>>>>>> I have been thinking about it myself,
>>>>>>>>
>>>>>>>> so what you could do is take the 80m xcvr and
>>>>>>>>
>>>>>>> modify/adapt it to work on
>>>>>>>> 40m.
>>>>>>>>
>>>>>>>> Any radio can be made to work anywhere, its just a
>>>>>>>>
>>>>>>> matter of how much
>>>>>>>> time, money & effort you want to put into it.
>>>>>>>>
>>>>>>>> cheers,
>>>>>>>>
>>>>>>>> Steve VK2KFJ, Sydney Australia. http://www.qsl.net/vk2kfj/
>>>>>>>>
>>>>>>>>
>>>>>>>> --- On Tue, 23/6/09, Jamie Campbell - VK2YCJ <vk2ycj at bravo.net.au>
>>>>>>>>
>>>>>>> wrote:
>>>>>>>
>>>>>>>>> From: Jamie Campbell - VK2YCJ <vk2ycj at bravo.net.au>
>>>>>>>>> Subject: [OZAPRS] HF Gateways
>>>>>>>>> To: Ozaprs at aprs.net.au
>>>>>>>>> Received: Tuesday, 23 June, 2009, 6:21 PM
>>>>>>>>> Gudday,
>>>>>>>>>
>>>>>>>>> If one was going to build a dedicated box (rx/tx)
>>>>>>>>>
>>>>>>> and
>>>>>>>
>>>>>>>>> antenna system for the car for APRS, what would be
>>>>>>>>>
>>>>>>> the most
>>>>>>>
>>>>>>>>> appropriate HF band to use ? 40m, 30m, 20m
>>>>>>>>> ?
>>>>>>>>>
>>>>>>>>> Does anyone ever use 80m for APRS ? Why
>>>>>>>>> not ?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The boys at the Mid North Coast Amateur Radio Club
>>>>>>>>>
>>>>>>> (
>>>>>>>>> http://www.mncarg.org ) have recently bought some kits
>>>>>>>>> for a small 80m 5W SSB Tranceiver. It's a very
>>>>>>>>>
>>>>>>> neat
>>>>>>>
>>>>>>>>> little kit and costs about $150. At that price
>>>>>>>>>
>>>>>>> and
>>>>>>>
>>>>>>>>> size it would be ideal for a standalone APRS box,
>>>>>>>>>
>>>>>>> but I am
>>>>>>>
>>>>>>>>> not sure if the kit is available for other bands.
>>>>>>>>>
>>>>>>>>> Any comments or suggestions appreciated.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks ...
>>>>>>>>>
>>>>>>>>> Jamie Campbell
>>>>>>>>> vk2ycj at bravo.net.au
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> You'll never reach your greatest potential if you
>>>>>>>>>
>>>>>>> walk
>>>>>>>
>>>>>>>>> past the dishwasher without emptying it or leave
>>>>>>>>>
>>>>>>> your
>>>>>>>
>>>>>>>>> costume on the bathroom floor.
>>>>>>>>>
>>>>>>>>> (Nancy-Bird Walton, Australian Aviatrix,
>>>>>>>>>
>>>>>>> 1915-2009)
>>>>>>>
>>>>>>>>> _______________________________________________
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>>>>>>>>> Ozaprs at aprs.net.au
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>>>>>>>>>
>>>>>>>>>
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>>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
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>>>>>
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