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#275272 - 05/29/15 09:00 PM Re: What radio bands to monitor? [Re: LesSnyder]
bws48 Offline
Old Hand

Registered: 08/18/07
Posts: 814
Loc: Anne Arundel County, Maryland
Excellent explanation!

For VHF, height and the proper antenna design are key.

But for which radio bands to monitor, the individual circumstances can give you reception while someone close to you cannot receive anything. And even with FM, strange (but uncommon) atmospherics can give you reception even though you are way out of line of sight from the transmitter (say 50 to 70 miles). I personally have heard VHF signals from hundreds of miles away; not predictably, but it happens.

While I think there must be better versions today, at home I still have an ancient Zenith multi-band radio (AM, FM and multiple HF and other bands) and a small Grundig multi-band radio.

In a really bad scenario, I don't think VHF FM will be useful: IMO, HF frequencies will be key. They have global reach without satellites, cable or repeaters. All you need is a transmitter and a receiver set to the right frequencies.

In case you are interested in the long range possibilities of HF in a crisis situation, it appears (reasonably possible and likely) that HF voice transmissions from Amelia Earhart were received by a young girl (Betty), in Florida. USA, after Earhart made a safe landing on Howland Island's reef. See: http://tighar.org/Projects/Earhart/Archives/Archivessubject.html
and scroll down to "radio distress calls" for several articles discussing Betty's evidence.
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#275273 - 05/29/15 09:31 PM Re: What radio bands to monitor? [Re: Mark_R]
Mark_R Offline
Old Hand

Registered: 05/29/10
Posts: 841
Loc: Southern California
I'm more interested in local situational awareness, without waiting the hour plus for the radio to broadcast it, then MF or HF skips off of the ionosphere. Besides, anybody who was unlucky enough to pick me up would have to wade through my painfully slow morse code.

-.- -. --- .-- .-- .... .- - .. -- . .- -. ..--..


Edited by Mark_R (05/29/15 09:41 PM)
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#275274 - 05/29/15 10:20 PM Re: What radio bands to monitor? [Re: bws48]
Tom_L Offline
Addict

Registered: 03/19/07
Posts: 690
Originally Posted By: bws48
In a really bad scenario, I don't think VHF FM will be useful: IMO, HF frequencies will be key. They have global reach without satellites, cable or repeaters. All you need is a transmitter and a receiver set to the right frequencies.


True, however, HF reception is extremely dependent on solar activity and ionospheric conditions. These vary a lot and in fact, have not been all that great recently (and for a few years already). So that is one thing that needs to be taken into account.

As far as radio in general, antenna is key in any band, regardless of your basic setup. In some ways, VHF/UHF is easier to work with because the proper antenna length is short and easy to manage. If you can get to a higher altitude, hopefully with a clear field of view, it will improve reception by an incredible margin. Even a cheap, low powered 0.5W PMR/FRS radio can reach out well beyond 50 miles under ideal conditions. In fact, the current PMR long-distance record is 333 miles. (Not that I would ever count on that sort of performance, but it does happen.)

HF on the other hand requires a very long antenna to work well. Now, even a 100ft spool of wire suspended on poles or trees will do fine for starters, but it is not very practical if you're on the move. So for really good long range performance HF reception works best with a stationary setup. And alas, only at night. During the daylight hours a basic multiband/HF receiver might have a pretty hard time picking up anything useful.

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#275275 - 05/30/15 12:27 AM Re: What radio bands to monitor? [Re: Mark_R]
LesSnyder Online   content
Veteran

Registered: 07/11/10
Posts: 1471
Loc: New Port Richey, Fla
re: antennas., AN/FLR9... gratuitous picture of my old duty station, 6922nd Security Group, Clark AFB, Philippines...once upon a time these HF direction finding stations ringed the Bear and Dragon... most have been dismantled since the end of the cold war





Edited by LesSnyder (05/30/15 12:27 AM)

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#275276 - 05/30/15 12:59 AM Re: What radio bands to monitor? [Re: Tom_L]
Mark_R Offline
Old Hand

Registered: 05/29/10
Posts: 841
Loc: Southern California
Originally Posted By: Tom_L


True, however, HF reception is extremely dependent on solar activity and ionospheric conditions. These vary a lot and in fact, have not been all that great recently (and for a few years already). So that is one thing that needs to be taken into account.


We're coming off of the peak of the 11 year sunspot cycle. Could that be monkeying with the ionosphere conditions?



Edited by Mark_R (05/30/15 01:00 AM)
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Hope for the best and prepare for the worst.

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#275278 - 05/30/15 03:08 AM Re: What radio bands to monitor? [Re: LesSnyder]
chaosmagnet Online   content
Sheriff
Carpal Tunnel

Registered: 12/03/09
Posts: 2796
Loc: USA
Originally Posted By: LesSnyder
I don't know your age, but pre cable TV antennas were Yagi... with several distinct lengths of elements pre cut for a particular TV channel frequency (ABC,CBS,NBC)... and a smaller 8 or so element nose for the UHF/VHF networks... an antenna rotor was used to orient them


That's not exactly how a Yagi works, there's a really good article at http://en.m.wikipedia.org/wiki/Yagi-Uda_antenna .

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#275284 - 05/30/15 03:14 PM Re: What radio bands to monitor? [Re: Mark_R]
Nomad Offline
Addict

Registered: 05/04/02
Posts: 457
Loc: Just wandering around.
Here is a link from the FCC that shows all licensed station within a user specified distance from a user supplied location. Insert your location (lat/lon) and try 25 miles for a starter.

http://fjallfoss.fcc.gov/General_Menu_Re...;wild_select=on

It is a bit of a technical babble but you can get a good idea of the interesting sites in your area and the type of gear you will need to monitor them.

If you are technically inclined, I suggest one of the software defined radio dongles that plug into your computer. Cheap, $20 or so. They provide a "waterfall" display of a wide segment of frequencies. You click on one and it decodes it. CW, RTTY, PSK, P25 (common digital audio used in most public service systems) and much much more. If you are an old tyme radio guy, this will really change your understanding of radio. Very impressive gadget.

Some really good educational stuff out there about software defined radio. Once you get up to speed (not hard) with this technology you will never even consider getting a dedicated scanner.

Most only work 30Mhz to 2ghz. Need to play games if you want below 30Mhz.



Edited by Nomad (05/30/15 03:15 PM)
Edit Reason: forgot to include link.
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#275285 - 05/30/15 05:23 PM Re: What radio bands to monitor? [Re: LesSnyder]
bws48 Offline
Old Hand

Registered: 08/18/07
Posts: 814
Loc: Anne Arundel County, Maryland
Originally Posted By: LesSnyder
re: antennas., AN/FLR9... gratuitous picture of my old duty station, 6922nd Security Group, Clark AFB, Philippines...once upon a time these HF direction finding stations ringed the Bear and Dragon... most have been dismantled since the end of the cold war


And I was a USASA Field Station Augsburg (mid-70's), Gablingen Kaserne, Augsburg Germany (aka "Home of the Professionals"). We also had the AN/FLR-9. photo here:

http://upload.wikimedia.org/wikipedia/commons/2/2d/Abh%C3%B6ranlage_Gablingen.JPG

One very vivid memory I have is driving with one of the maintenance WO's into the center ring in his car with the car radio on. Great reception outside the ring, none at all after getting past the inner ring. These things really sucked up the RF energy.
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#275286 - 05/30/15 06:16 PM Re: What radio bands to monitor? [Re: Nomad]
Russ Online   content
Carpal Tunnel

Registered: 06/02/06
Posts: 4594
Loc: SOCAL
Thanks Nomad, this sounds interesting. Do you have a link for a "software defined radio dongle" you recommend.

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#275287 - 05/31/15 02:22 AM Re: What radio bands to monitor? [Re: Mark_R]
Mark_R Offline
Old Hand

Registered: 05/29/10
Posts: 841
Loc: Southern California
I think he's talking about something like these.
www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Telescopic/dp/B00QFCNNV0

I'm not sure how much good it would do while moving due to battery life of a laptop. But while stationary, and if it could handle CTCSS tones and trunking, it would provide critical information well ahead of the radio.
_________________________
Hope for the best and prepare for the worst.

The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane

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