[OZAPRS] On possibilities with short HF whips

vk4tec at tech-software.net vk4tec at tech-software.net
Fri Dec 8 20:33:08 AEDT 2017


What a bright spark 

-----Original Message-----
From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Glen English VK1XX
Sent: Friday, 8 December 2017 6:18 PM
To: ozaprs at aprs.net.au
Subject: Re: [OZAPRS] On possibilities with short HF whips

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-acce
>>> ss/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
>>>
>>> _______________________________________________
>>>                      OZAPRS mailing list
>>>                      OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au> 
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>> _______________________________________________
>>>                      OZAPRS mailing list
>>>                      OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au> 
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>> _______________________________________________
>>>                  OZAPRS mailing list
>>>                  OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au> 
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>> _______________________________________________
>>>                  OZAPRS mailing list
>>>                  OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au> 
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>>
>>>              _______________________________________________
>>>              OZAPRS mailing list
>>>              OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>>             http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>>              _______________________________________________
>>>              OZAPRS mailing list
>>>              OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>>             http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>>
>>>
>>>          _______________________________________________
>>>          OZAPRS mailing list
>>>          OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>>         http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>> <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>>
>>>
>>>      _______________________________________________
>>>      OZAPRS mailing list
>>>      OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>>     http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>>      <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>      _______________________________________________
>>>      OZAPRS mailing list
>>>      OZAPRS at aprs.net.au <mailto:OZAPRS at aprs.net.au>
>>>     http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>>      <http://lists.aprs.net.au/mailman/listinfo/ozaprs>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> OZAPRS mailing list
>>> OZAPRS at aprs.net.au
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>
>>
>> _______________________________________________
>> OZAPRS mailing list
>> OZAPRS at aprs.net.au
>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>
>>
>> _______________________________________________
>> OZAPRS mailing list
>> OZAPRS at aprs.net.au
>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>
> _______________________________________________
> OZAPRS mailing list
> OZAPRS at aprs.net.au
> http://lists.aprs.net.au/mailman/listinfo/ozaprs


_______________________________________________
OZAPRS mailing list
OZAPRS at aprs.net.au
http://lists.aprs.net.au/mailman/listinfo/ozaprs



More information about the OZAPRS mailing list