[OZAPRS] On possibilities with short HF whips
vk2tv
vk2tv at exemail.com.au
Sat Dec 9 08:01:56 AEDT 2017
Glen,
Being Brisbane it would have been 25kv, they never had a 1500V system
although that voltage was discussed on two occasions but never adopted.
Ray vk2tv
On 08/12/17 19:18, Glen English VK1XX wrote:
> Ian was it 1500V overhead, or the now days 25kVAC ?
>
>
> On 8/12/2017 6:32 PM, Ian Bennett wrote:
>> I remember back in the 80's when I was in uniform and in Brisbane, a
>> radio vehicle drove over the railway line near Enoggera with the HF
>> whip still up. Made a BIG flash (apparently), blew a tyre, shutdown
>> the train network for an hour or so and welded the 106 to it's mount.
>> I have two HF whips mounted on the bullbar of my 100 Series; my home
>> made APRS antenna is just shy of 2m long (that was the length of the
>> donor antenna that I dismantled) and is 3150(ish) mm floor to tip. I
>> haven't had any dramas like the one mentioned above however I tie
>> them back when negotiating "tight" spaces.
>> Will be a different story when we get our truck based motorhome but I
>> have a cunning plan for that ;-)
>>
>> Ian
>>
>> On 08/12/17 17:39, Mathew McKernan wrote:
>>> I did similar with a Codan autotune on my Landcruiser, mounted above
>>> the spare wheel carrier connected to my Codan 9323.
>>>
>>>
>>> Hit the line at the same spot... was waiting for smoke to fill the
>>> cabin. I was pleased it didn't, but disappointed as it would have
>>> been pretty impressive!
>>>
>>> ----------------------------------------------------------------------------------------------------
>>>
>>> *From:* OZAPRS <ozaprs-bounces at aprs.net.au> on behalf of Glen
>>> English VK1XX <glenlist at pacificmedia.com.au>
>>> *Sent:* Friday, 8 December 2017 5:26:29 PM
>>> *To:* ozaprs at aprs.net.au
>>> *Subject:* Re: [OZAPRS] On possibilities with short HF whips
>>> what are the recommendations and user practical limits for Melbourne ?
>>> (trams)
>>>
>>> Canberra here you'll get into trouble ~ 4m
>>>
>>> I had the loop on my vehicle when I was driving in Melbourne a fair
>>> bit....
>>>
>>> I once hit a tram line with my car roof antenna heatshrink insulated
>>> helical at Racecourse Road, Kensington... it made a huge pop in the
>>> receiver but otherwise no damage...
>>>
>>>
>>>
>>>
>>> On 8/12/2017 3:07 PM, Matthew Cook wrote:
>>>> This is also worth considering when looking at larger HF whips.
>>>>
>>>> http://www.rms.nsw.gov.au/business-industry/heavy-vehicles/road-access/restricted-access-vehicles/4-6m-high.html
>>>>
>>>>
>>>> Each state has their own variations to the above, nationally
>>>> un-restricted is 4.3m.
>>>>
>>>> 73
>>>>
>>>> Matthew
>>>> VK5ZM
>>>>
>>>> On 8 December 2017 at 14:03, Graeme <graeme at abrona.com.au
>>>> <mailto:graeme at abrona.com.au>> wrote:
>>>>
>>>> Thanks Glen.
>>>>
>>>> Obviously my decision against buying a 2.2m centre loaded 40m
>>>> whip
>>>> because it would bend in the wind to its disadvantage in
>>>> favour of
>>>> a base loaded 1.4m whip wasn't a good one for multiple reasons.
>>>>
>>>> Graeme 2HFG
>>>>
>>>> -----Original Message----- From: Glen English VK1XX
>>>> Sent: Friday, December 8, 2017 10:19 AM
>>>> To: ozaprs at aprs.net.au <mailto:ozaprs at aprs.net.au>
>>>> Subject: Re: [OZAPRS] On possibilities with short HF whips
>>>>
>>>>
>>>> Ran some NR predictions for 10 MHz for Brisbane Sydney, and 7
>>>> and 3.5
>>>>
>>>> and also some more details calcs on the Diamond 1.4m logn base
>>>> loaded whip
>>>>
>>>> turns out to be ~ 3% efficiency.
>>>>
>>>> for the -15dBi TX terminal (1.4m base loaded whip with suboptimal
>>>> loading Q)
>>>>
>>>> yep, in daytime, single hop 750-1200km , 100W into the antenna,
>>>> expect
>>>> around 15dB SNR for the 300 baud modem given a good receiver
>>>> antenna and
>>>> setup...with a modem like DireWolf that can cope with frequency
>>>> variations. Be sure you know your radio frequency offset before
>>>> you start.
>>>>
>>>> with same length whip on 7 MHz, expect about 300-700km in
>>>> daylight, but
>>>> not much use outside that time and distance.
>>>>
>>>> All of this means is for 300 baud FSK packet mode and 100W, the
>>>> mode is
>>>> unsuitable for low efficiency mobile antennas like base loaded
>>>> short
>>>> whips. (3% or less efficiency at 10 MHz, 2% at 7 MHz etc)
>>>>
>>>> All this points to: (in my opinion) needing a >=2.2m long whip
>>>> instead
>>>> of a 1.4m long whip.
>>>> and an antenna with a non base loaded structure (for 300 baud
>>>> packet)
>>>>
>>>> Get your antenna efficiency up to 10% at 7 MHz and then now you
>>>> have an
>>>> idea setup 24 hours, single freq .... 10 MHz almost good
>>>> enough except
>>>> for the wee hours 2am-sunrise when you will be asleep anyway.
>>>>
>>>> So the lesson here, 300 baud packet needs decent antenna
>>>> efficiencies
>>>> mobile.
>>>> hence the need for a mode that does about 6dB better
>>>>
>>>> sure we can do alot better than 6dB, but 6dB better mode is
>>>> what is
>>>> required to work on the 1.4m base loaded whips.
>>>>
>>>> Otherwise for 300 baud FSk packet, it needs to be teamed up with
>>>> antenna
>>>> efficiency >= 8%, implying something with a feedpoint of
>>>> around 2
>>>> ohms
>>>> Rr and not too lossy loading and matching... a whip of 2 meters
>>>> tall at
>>>> 10 MHz with continuous or 1/3 loaded structure. Base loaded
>>>> structures
>>>> are the worst !
>>>>
>>>> The longer 1.8m long CB helical whips are a bit hard to find
>>>> these
>>>> days.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> g
>>>>
>>>>
>>>> On 7/12/2017 6:36 PM, Glen English VK1XX wrote:
>>>>
>>>> ok
>>>>
>>>>
>>>> On 7/12/2017 6:24 PM, vk4tec at tech-software.net
>>>> <mailto:vk4tec at tech-software.net> wrote:
>>>>
>>>> You are not telling me anything new
>>>>
>>>> -----Original Message-----
>>>> From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au
>>>> <mailto:ozaprs-bounces at aprs.net.au>] On Behalf Of Glen
>>>> English VK1XX
>>>> Sent: Thursday, 7 December 2017 5:10 PM
>>>> To: ozaprs at aprs.net.au <mailto:ozaprs at aprs.net.au>
>>>> Subject: Re: [OZAPRS] Hf gates CD
>>>>
>>>> base station 700-1500km away will hear you, but you wont
>>>> hear a station 50km away.
>>>>
>>>>
>>>> On 7/12/2017 5:57 PM, vk4tec at tech-software.net
>>>> <mailto:vk4tec at tech-software.net> wrote:
>>>>
>>>> Go for a walk
>>>>
>>>> -----Original Message-----
>>>> From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au
>>>> <mailto:ozaprs-bounces at aprs.net.au>] On Behalf Of
>>>> Glen
>>>> English VK1XX
>>>> Sent: Thursday, 7 December 2017 4:55 PM
>>>> To: ozaprs at aprs.net.au <mailto:ozaprs at aprs.net.au>
>>>> Subject: Re: [OZAPRS] Hf gates CD
>>>>
>>>> tracker might well have CD but:
>>>>
>>>> 1) Consider that in the mobile, you wont hear any
>>>> stations less than the skip distance (unless they are
>>>> 10km away) . The daytime skip distance might be
>>>> 700km.... so anyone inside that distance you wont
>>>> hear cause the ionosphere wont support it..it wont
>>>> support any angles higher than perhaps 45 degrees.
>>>>
>>>> The base station though will hear lots of
>>>> transmissions from lots of stations >700km to 1500km
>>>> away, so there would be significant collision chance
>>>> if the position update is too often. Maybe 10 minutes
>>>> might be suitable. I dunno why people run..
>>>>
>>>> 2) With a 5% to 10% efficiency mobile you wont hear
>>>> too much unless the propagation is optimal...
>>>>
>>>>
>>>> glen
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 7/12/2017 5:41 PM, vk4tec at tech-software.net
>>>> <mailto:vk4tec at tech-software.net> wrote:
>>>>
>>>> Blind ?
>>>>
>>>> Tracker has CD
>>>>
>>>> -----Original Message-----
>>>> From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au
>>>> <mailto:ozaprs-bounces at aprs.net.au>] On Behalf Of
>>>> Glen English VK1XX
>>>> Sent: Thursday, 7 December 2017 2:46 PM
>>>> To: ozaprs at aprs.net.au
>>>> <mailto:ozaprs at aprs.net.au>
>>>> Subject: Re: [OZAPRS] Hf gates
>>>>
>>>> but how does this matter?
>>>>
>>>> You will be transmitting on a frequency blind
>>>>
>>>> there will be receivers you cannot control
>>>>
>>>> There will be any number of propagation modes you
>>>> cannot control...
>>>>
>>>>
>>>>
>>>> On 7/12/2017 3:34 PM, Andrew Rich wrote:
>>>>
>>>> Hi
>>>>
>>>> Can I get a list of hf gates on 10.147
>>>>
>>>> In my planning for the Xmas run
>>>>
>>>> Cheers
>>>>
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>>>
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