Difference between revisions of "User talk:W0DBW"

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  kd0cvg Ed Omaha NE
 
  kd0cvg Ed Omaha NE
  
== tropospheric ducting ==
+
==VHF Propagation==
 
+
===tropospheric ducting===
 
+
 
[http://www.engineeringradio.us/blog/2010/05/e-skip-tropospheric-ducting-and-other-vhf-propagation-phenomena/ E-skip, tropospheric ducting and other VHF propagation phenomena]
 
[http://www.engineeringradio.us/blog/2010/05/e-skip-tropospheric-ducting-and-other-vhf-propagation-phenomena/ E-skip, tropospheric ducting and other VHF propagation phenomena]
 
By Paul Thurst
 
By Paul Thurst
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Occasionally, solar storms will effect communications on all frequencies. The last time I heard this was in the last sun spot peak around 2000 or so. I was listening to the radio and all the stations faded for several seconds. It turns out a huge solar flare had erupted and send a stream of particles through the Earth’s atmosphere.  I happened to be driving down the road and immediately my cell phone started ringing.  Listening to the panicked program director on the other end, you’dve thought the earth has stopped spinning on it’s axis.  Anyway, it does happen once in a while.
 
Occasionally, solar storms will effect communications on all frequencies. The last time I heard this was in the last sun spot peak around 2000 or so. I was listening to the radio and all the stations faded for several seconds. It turns out a huge solar flare had erupted and send a stream of particles through the Earth’s atmosphere.  I happened to be driving down the road and immediately my cell phone started ringing.  Listening to the panicked program director on the other end, you’dve thought the earth has stopped spinning on it’s axis.  Anyway, it does happen once in a while.
 
Be Sociable, Share!
 
Be Sociable, Share!
 +
 +
===VHF Propagation Map===
 +
link: [http://aprs.mountainlake.k12.mn.us/ VHF Propagation Map]

Revision as of 18:36, 23 July 2017

articles to read

explore

My new CLICK ME banner

Ke0etzvisitpage.png

USED MARKET PRICE WATCH

$336   2015    Alinco DX-70T                   Used fair condition
$390   2015    Alinco DX-70T                   Used excellent condition
$391   2014    Alinco DX-70T                   Used excellent condition

$150   2014    Drake TR-7                      Used fair condition
$366   2015    Drake TR-7                      Used fair condition
$400   2014    Drake TR-7                      Used good condition
$430   2015    Drake TR-7                      Used excellent condition

$425   2015    ICOM IC-718 HF                  Used excellent condition
$435   2015    ICOM IC-718 HF                  Used excellent condition
$485   2015    ICOM IC-718 HF                  Used excellent condition
$371   2015    ICOM IC-735                     Used good condition
$380   2015    ICOM IC-735                     Used good condition
$385   2015    ICOM IC-738                     Used good condition
$395   2015    ICOM IC-751A                    Used good condition

$658   2015    Kenwood TS-850SAT               Used excellent condition
$685   2015    Kenwood TS-850SAT               Used excellent condition
$615   2015    Kenwood TS-940S                 Used excellent condition

$340   2014    Yaesu FT 840                    Used excellent condition
$321   2015    Yaesu FT 8900 Quad Band         Used excellent condition
$610   2015    Yaesu FT 897                    Used excellent condition
$511   2015    Yaesu FT-990                    Used good condition
$575   2015    Yaesu FT-990                    Used excellent condition
$592   2015    Yaesu FT-990                    Used excellent condition
$610   2015    Yaesu FT-990                    Used excellent condition
$655   2015    Yaesu FT-990                    Used refurbished 

BASED ON KNOWN PRICE RANGES

$330 - $390    Alinco DX-70T
$330 - $510    Icom IC-2820H

NISSEI RS-502

SWR/POWER METER with 5/20/200W scale 1,8-525MHz with monitoring forward power, reverse power and SWR reading.

P06-402.gif

Main features: Large meter display for ease of reading, Forward RF power readings, switchable to indicate either AVG average, power or Peak Envelope Power(PEP) for SSB and AM transmitters, Reflected RF Power readings, VSWR ratios and calibration meter, Dual connectors SO-239: 1,8-200MHz and 125-525MHz. I/O Impedance: 50 ohm, Illuminated meter.

Weight: 0,950Kgr. Dimensions: 190x85x135 mm.

MFJ-874

This looks a lot like the Nissei, however, is MFJ brand. This has one extra button to select VHF/UHF or HF.

MFJ-874Meter.jpg

Diamond SX-400

Diamond power meter SX-400 5w 20w 200w 400w Power and SWR Meter - The SX400 measures forward and reflected power and VSWR. Compact size makes meter useful for testing both base and mobile installations.

Diamondsx400.jpg

Special Features: Illuminated meter, Switchable r.m.s. or peak power, Measures forward, reflected & VSWR power. Dimensions 6"W x 2"H x 4"D, 2 lbs.

Specifications: 140-525 MHz at 5, 20, or 200 watts. Connector SO-239, Minimum power required to SWR test is 4 watts.

Merchants

Online merchants

Many merchant reviews can be found at the eHam Company Reviews forum from other HAM operators sharing their experiences.

club equipment

Some of the equipment I was able to operate by the kind provision of our local radio club.

  • Kenwood TS-450S

Kenwoodts450s.jpg

Drake TR-7

later model with a serial number 89xx

Software Defined Radio (SDR)

  • SoftRock RXTX 30-20-17 meter SDR transceiver QRP
  • SoftRock RXTX 15-12-10 meter SDR transceiver QRP

GMSK(digital)

Gaussian Minimum Shift Keying or Gaussian filtered Minimum Shift Keying, GMSK, the form of modulation with no phase discontinuities used to provide data transmission with efficient spectrum usage.

  • Icom ID-800H Digital Dual Band Mobile Transceiver with D-Star

Purchase Consideration

Equipment I do not own but have been researching and in consideration for purchasing. If I make a purchase I will use and follow up with a review of the product. We like to do product reviews here.

Test Equipment

I like the roller inductor style operation of antenna tuners for HF, however, I don't need a model that handles 1.21 gigawatts! Been looking around to see if there is a less expensive version of these.

Also noticed MFJ gets a lot of negative reviews. Our club uses MFJ tuners, they seem to work.

  • MFJ 969 Antenna Tuner - has roller inductor. $200 new. 6 thru 160 Meter HF Bands (1.7Mhz To 55Mhz). 300 Watts.
  • MFJ-986 Antenna Tuner - roller inductor, high wattage. $330 new. 1.8 - 30 MHz, 3000 Watts

Transceivers

ICOM IC-736 - 160 to 6 meter

Expand your horizons to 6 meters with the Icom IC-736. It also covers 30, 17 and 12 meters. This all band transceiver features a 500 kHz to 30 MHz general coverage receiver. The 736 has a built-in HF and 6 meter antenna tuner. Enjoy 5 to 100 watts full duty RF power input in SSB/CW/FM (40W AM) modes, even on 6 meters. For CW operators full and semi break-in is supported.

Icomic736xceiver.gif

160-6 Meter Transceiver w/built-in tuner . Maybe in production? Absence of receive coverage from 30MHz to 45MHz. 6-meter is technically (50-54 MHz) so the gap exists in non Ham freqs. The lack of receive between 30MHz and 45MHz and the CW tuning arrangement are the most notable disadvantages.

Information on Universal-Radio Discontinued HF Transceivers including band coverage.


Icom IC-718 HF - A Modern Full Mode HF Transceiver

This one is still in production. It's straightforward easy to operate modern HF rig.

0.03-29.999999 MHz* general coverage receive capability. *Guaranteed range: 0.5-29.999999 MHz


Yaesu FT 980

The Yaesu FT-980 is a deluxe HF transceiver covering 160 to 10 meters amateur bands in SSB, CW, FM and AM Modes. This radio features two independent receiver front ends. One is for general coverage receive from 150 kHz to 29.99999 MHz and the other for the amateur bands only. Seven JFETs are employed to provide extraordinary dynamic range. Ten VCOs are used over the local signal range to secure a low carrier-to-noise ratio. A three-step attenuator is provided to deal with the very strong signals. The triple conversion design incorporates four cascaded stages of IF filtering for all modes. Twelve memory channels are available. Using push-pull MRF422 final transistors, rated at 280 watts each, the transmitter coasts along at 100 watts output. Full break-in QSK is provided for CW operation.

I'm not a fan of push button and menus. I like independent pots.


TYT TH-9800 Quad Band

TRANSCEIVER, 29/50/2M/70CM, CROSS BAND, 50 WATT - Yeah one of them there CHINA knockoffs. However, for the price this little guy does a lot. I've read quality many vary widely as is the case with this Chinese stuff. I am looking at one now that has been fully tested at a shop in the United States. They are also being sold on Amazon.com


Scanners

Antennas

2m/440 dual band needed for VHF UHF operation.

mobile:

  • Larsen NMO2/70

base station:

  • J-Pole for 2-meters and 70-cm - can be built "homebrew" which I like to do.
  • DIAMOND X-50 2m/440 ANTENNA
  • Cushcraft Ringo Ranger Vertical Antennas ARX2

6-meter

Below 10-meter

Technician Class on HF below 50MHz

SSB (Single Sideband)

  • 10-meters 28.300 – 28.500

CW Morse Code

  • 80-meters 3.525 – 3.600
  • 40-meters 7.025 – 7.125
  • 15-meters 21.025 – 21.200
  • 10-meters 28.000 – 28.500

resources:

Plattsmouth Police and Trunktracking

Frequency  	License  	Type  	Tone  		Alpha Tag  	Description  			Mode  	Tag
----------------------------------------------------------------------------------------------------------------------------
853.30000  	WQET706  	RM 	156.7 PL 	CassSoNEDisp 	Sheriff - Plattsmouth Tower  	FMN  	Law Dispatch 
853.87500  	WQET706  	RM 	048 NAC 	CassSoSEDisp 	Sheriff - Murray Tower  	P25  	Law Dispatch
39.68000  	WZC542  	M 			CassSo C2C 	Sheriff Car to Car  		FM  	Law Talk
153.89000  			BM 	123.0 PL 	Cass Co Jail 	Cass County Jail  		FMN  	Corrections 
154.38500  	WNXN466  	RM 	114.8 PL 	Cass Co Fire 	County Fire Dispatch  		FMN  	Fire Dispatch 
151.10000  	KIZ260  	RM 	110.9 PL 	CassCoRoads1 	Highway Dept. 1  		FM  	Public Works 
151.10000  	KIZ260  	RM 	465 DPL 	CassCoRoads2 	Highway Dept. 2  		FM  	Public Works
851.40000  	WQET706  	RM 	156.7 PL 	Platts PD-A 	Police - Analog  		FMN  	Law Dispatch 
851.40000  	WQET706  	RM 	048 NAC 	Platts PD-D 	Police - Digtial  		P25  	Law Dispatch 
39.76000  	KSQ696  	M 			PlattsPD-Car 	Police 4 - Car to Car  		FMN  	Law Talk 
155.49000  	KSQ696  	BM 	107.2 PL 	PlattsPD-VHF 	Police  			FM  	Law Dispatch 
159.25500  	WPSF346  	RM 	606 DPL 	Platts FD 1 	Fire Dispatch  			FMN  	Fire Dispatch 
153.92000  	WPSF346  	M 	565 DPL 	Platts FD 2 	Fire TAC 1  			FMN  	Fire-Tac 
158.88000  	WPSF346  	M 	654 DPL 	Platts FD 3 	Fire TAC 2  			FMN  	Fire-Tac 
----------------------------------------------------------------------------------------------------------------------------

antenna height calculator

antenna analyzer

Software Antenna Analyzer

  • MAX6 - 1 MHz up to 500 MHz, Get the 8 button version
  • W4RT miniVNA / mini Radio Solutions miniVNA - 0.1 to 180 MHz, USB to PC ($400)
  • Timewave TZ-900s


Standalone Antenna Analyzer

  • AW07A HF/VHF/UHF sold under SainSonic and Feature Tech - $220 new w free shipping - also known as SainSonic RA-07A
  • Comet CAA-500MARKII Antenna Analyzer ($389.95) 1.8-500 MHz, LCD Color Screen, Dial Tune Knob, UHF & Type-N Connector, 8-16 V, Each

Additional Information

Look for hf vhf uhf antenna analyzer

Clear Channel Ranger AR-3500

I own a 100w model Clear Channel AR-3500. They were available in a lower 30w version (I think) and a more powerful 100w version. The 100w version has massive heatsink fins on the rear with the longest two on both ends. It is easy to tell them apart. I have been thinking about selling it as I no longer do much on 10-meter. I've been watching prices to get an idea of what I would want for mine if I decide to sell it.

CLEAR CHANNEL RANGER AR-3500 100W MODEL USED PRICES

$233   2015    Clear Channel Ranger AR-3500        Used fair condition
$255   2015    Clear Channel Ranger AR-3500        Used good condition
$289   2015    Clear Channel Ranger AR-3500        Used fair condition
$332   2015    Clear Channel Ranger AR-3500        Used good condition

My Kenwood Part 90 Radios

Kenwood TK 880H

  • Frequency: UHF
  • Band: 450-490 Mhz
  • Power: 40 Watts
  • Channels: 600
  • Narrow Band: Yes

Kenwood TK 380

  • UHF TK-380K 512 Channel Radio (w/Version 2.0 Firmware)
  • High Capacity Battery - NEW (NiCd, 1500 mAh, KNB-17 Compatable)
  • Desk Top Charger (KSC-15)
  • Standard Antenna (UHF Low Profile Helical - KRA-27M)
  • Spring Action Belt Clip (KBH-10)

Coaxial Cable Index

See: Coax Cable for Ham Radio Applications

Microreader

decodes cw and displays text. listen to cw without knowing Morris code.

  • ERA Microreader MKII CW Decoder - a stand alone solid state cw decoder circa 1980s that works well.

MFJ Tuners

  • MFJ-906 - 6m tuner
  • MFJ MFJ-921 - 2m/1.25m tuner

Tools You Will Need for Electronic Service

  • Desoldering pump - desolder vacuum to remove heated solder
  • Helping hand - weighted base and clamps to hold boards into place

November 2015 Log

11/22/2015 kc0mfw on 146.790

146.790 CRESTON is linked with other Iowa repeaters, including 442.400 ARISPE.

146.790 - K0CSQ 136.5	Creston	Iowa	Southwest Iowa Amateur Radio Association Repeater ...


442.400 with PL 151.400 +5Mhz offset

NOAA Iowa Skywarn repeater network.

aa0os
w0hn
n0vpr
n0gmh
n0fhq
n0oru
ka0rde - bedford
w0jw -
kb0nyg
w0sms - Bob
kd0twe - bedford
ke0efn - urbandale
kn0wme - des moines
kc0mfw - Jason
kd0mrd
kd0sj
kd0wrq
wk0ff
kb0owm
kb0nyh

local business frequency chart

Walmart on Cornhusker highway in Bellevue ... MURS 4 ... 154.570 MHz ... Blue Dot

Mobile Radio OOBM

YAESU FT-7900R .......... OOBM(yes) ............. G(unknown)
Yaesu FT-857D ........... OOBM(yes) ............. G(unknown)
Kenwood TM 733A ......... OOBM(yes) ............. G(yes)

AREA NETS (unknown status)

Monday

7:00 PM 	145.29 	South-West Iowa ARES Glenwood, IA.
8:00 PM 	144.25 	NE Missouri SWOT.
9:00 PM 	146.94 	AARC Chat Net. Ak-Sar-Ben ARC Omaha, NE.
 	  	 

Tuesday

7:00 PM 	147.36 	QCWA Net, Chapter 210 (seasonal, October through March).
8:00 PM 	50.2 	6m SSB Net.
9:00 PM 	145.31 	Washington Co. ARES Washington Co, NE.
 	  	 

Wednesday

7:00 PM 	146.67 	Dodge Co. ARES Dodge Co, NE.
7:30 PM 	7.122 	CW Four State QRP Comfortable Net.
8:00 PM 	3.564 	CW Four State QRP Comfortable Net.
8:00 PM 	145.31 	Saunders Co. ARES Saunders Co, NE.
8:30 PM 	7.122 	CW Four State QRP Comfortable Net.
9:00 PM 	3.5805 	PSK Four State QRP Comfortable Net.
9:00 PM 	146.82 	Pottawattamie County ARES Council Bluffs, IA.
 	  	 

Thursday

8:30 AM 	7.122 	CW Four State QRP 40M Morning Net.
7:30 PM 	-145.31 	Lincoln/Omaha SATERN Net. Ashland, NE.
8:00 PM 	28.35 	10-Meter Net.
8:00 PM 	144.25 	2-Meter SSB Net.
8:00 PM 	146.36 	Heartland DX Association.
9:00 PM 	28.305 	10-Meter Net.
 	  	 

Saturday

12:00 PM 	146.82 	Swap Net Council Bluffs, IA.
8:30 PM 	3.921.000 	QCWA Chapter 20.
 	  	 

Sunday

8:00 AM 	3.902.500 	Swap Net.
8:30 AM 	3.896.500 	3900 Club.
8:30 PM 	443.925+ 	(103.5 tone) IRLP Net.
9:00 PM 	-146.94 	Douglas Co. ARES net, KØUSA repeater.

source: http://www.aksarbenarc.org/main/index.php/area-nets

field day

2016 ARRL Field Day is June 25-26

Grid Square Map

Links

http://gatorradio.org/Operating_Training_Aides/Ham_US_Grids%202005.pdf

https://www.qrz.com/gridmapper

HF NETS TO LOOK UP

14.300 maritime net

14.300 MHz has become a very well known frequency in the Amatuer Radio world. There are three major nets in the Western Hemisphere that operate on 14.300 MHz. From early morning until late evening the frequency is busy with traffiic of one form or another. Begining at 0700 ET daily, The Intercon Net, formally know as The Intercontinental Amatuer Traffic Net, starts out the day. Intercon runs until 1200 ET before handing the frequency over to The Maritime Mobile Service Network. The MMSN, which also runs daily, operates from 1200 ET until 9 PM EST / 10 PM EDT or 0200 UTC. After The MMSN raps up The Pacific Seafarers Net begins operation at 10 PM EST / 11PM EDT or 0300 UTC and runs various lengths of time, depending on traffic load, but usually about 2 hours or less.

YL International Single Sideband System

14.332 MHz net.

kq0j Joel provided this local net list

Mon-Fri     		0730       3.982   	NE Morning Net
Mon-Fri     		1230       3.982     	Cornhusker Net
Mon-Fri     		1300       7.282    	Nebraska Net
Mon-Fri     		1830       3.982     	NE Storm Net
Daily           	1930       1.995   	160 M Neb Wx net ( daylight savings time only)
Mon-Fri-Sunday     	2100     146.76     	Eastern NE ARES

Monday        		2100     146.94     	Aksarben Net

Tuesday     		2000      50.200  	6M Omaha area SSB Net

Wednesday     		2100     146.82     	Pottawattamie County ARES

Saturday     		1200     146.82     	Swap Net

Sunday         		2100     146.94     	Midlands ARES Net
Sunday         		0830       3.982   	ARES Net

Local D-star frequencies

145.175 Omaha KD0CGR/c
146.895 Papilion KA0OAU/c
442.125 Omaha KD0CGR/b
145.250 Lincoln W0MAO/c

Note: Omaha VHF and Lincoln is perma-linked to 2C

HF TUNER SETTINGS MFJ-941E

[10-meter convertable: short]
10m		7-K-4		100w		28.350 MHz

[10-meter convertable: attached]
20m  		7-K-0		100w
40m		3-I-0		100w
40m		0-I-0		100W		7.200 MHz
80m		6-E-0		 10w
[Fence Antenna]
80m		4-E-0		100w
80m		5-E-1		100w




3.868.040	<- Tuner Settings are: 3.6 x E x .4 on fence antenna

HT Antenna Test Results

		F8HP	NAG	SRH	TYT	888 
		DUCK	NA771	805S	WHIP	DUCK
443.4500	2.6	3.3	3.0	1.6	3.0
462.6785	2.9	4.9	8.8	2.9	3.4
147.0000	2.9	3.6/1.5	x	x	x
152.0000	4.8	2.6/1.9	x	x	x

H8HPDUCK	2.3 @ 446	@<2	x
NAGNA771	3.2 @ 445	@<2	x
SRH805S 	1.1 @ 426	@<2	412-436
TYTWHIP 	1.5 @ 445	@<2	430-453
888DUCK 	3.0 @ 450	@<2	x


NAGNA771 - ground provided though human body produces better SWR, see split results in table 1

x - indicates no resonance

1.25m 220 Repeater List

224.76
223.94 (omaha)
224.66 (fremont)
224.82 (omaha) wb0cmc
224.94 (omaha) xx0usa

Rich wa0zqg net list

If you’re new around here, one way to get acquainted is to visit a club meeting (4th Thurs 7:00PM at Co/Blfs Red Cross) or get in on some local nets like:

  • Sunday 7PM 145.29 R-
  • Sunday 8PM 145.13 R-
  • Sunday 9PM 146.94 R-
  • Monday 7PM 145.29 R-
  • Monday 9PM 146.94 R-
  • Tues 8PM 50.200 USB
  • Wed 730 145.13 R-
  • Wed 9PM 146.82 R-
  • Thurs 8PM 28.350 USB
  • Sat Noon Swap Net 146.82 R-

My new callsign takes longer to code

My new call sign has fewer characters to speak, however, I am curious how it is to tap out in code.

-.- . ----- . - --..		ke0etz		dah,dit,dah  dit  dah,dah,dah,dah,dah  dit  dah  dah,dah,dit,dit
.-- ----- -.. -... .--		w0dbw		dit,dah,dah  dah,dah,dah,dah,dah  dah,dit,dit  dah,dit,dit,dit  dit,dah,dah

Now, in my region we're all stuck with the five dah's, however, the rest of it can vary in what serious CWers consider a nice sign to code. The new call sign takes longer to tap in code because dahs consume more time than do dits.

HF Triplexer

Designed to allow the multiplexing of a single 10-15-20 meter triband antenna amongst two or three single band radios. It may be used for events such as Field Day, WRTC as well as multi-single, multi-multi and even advanced single op operations. No longer are separate antennas necessary to run multiple radios.

Comprised of three carefully designed two pole filters which, when combined, provides isolation between radio ports on 10, 15 and 20m, provided the antenna port is connected to an appropriate antenna.

It is not meant for use with a non-resonant antenna which needs a tuner to operate. Examples of antennas that are not usable with the triplexer are Steppirs, G5RV, monoband dipoles, non-resonant verticals, etc.

D-Star Notes

This is the web site that I registerd my callsign

You are not assigned a number as you ar with DMR DMARC. Wait about 24 - 48 hours.

The D-Star repeater is located: Downtown on the 1st Nat Bank building.


2m repeater is perm linked to 002C reflector .. one of 60 or more
The Omaha repeater is a "node" which connectors to a "reflector"
70cm dynamic but usually sits idle local communication.
K0OQL can login and change the 70cm repeater to whatever reflector.

DTRS goes to the APRS site.

Net: 1st and 3rd Wednesday of the month - D Star net 9:00pm twice a month


145.175 and you have to know the repeater callsign and deck. C is always VHF and B is UHF. Everything is 8 digits.

FCC Title 47 of the CFR

See: FCC Title 47 of the CFR

Idiots Say Break

220 Promote the Band Net

Friday, July 14, 2017

kd0vub     	Dave (NC)     	Papillion NE
kd0cvg		Ed		Omaha NE

VHF Propagation

tropospheric ducting

E-skip, tropospheric ducting and other VHF propagation phenomena By Paul Thurst

While the FM frequency band (88 to 108 mHz) is mostly line of sight, there are things that cause long distance reception hundreds or sometimes even thousands of miles from the transmitter. For a radio engineer, this can lead to all sorts of problems. Some serious like STL cut outs, and some quite funny, such as the general manager panicking when several new stations suddenly pop up in town. One of the many jobs of a broadcast engineer is to avoid problems and fix them if they show up (preferably the former).

The first and most common of these phenomena is Tropospheric ducting. This happens in warmer weather when there is a high pressure system nearby and is more prevalent over flat terrain. What happens is a warmer layer forms in the atmosphere above a cool layer. That is why it is also known as “temperature inversion.” This causes a higher refractive index, which means that normally the signal would carry on out into space, however, upon encountering this warm layer it is bent back to earth. It can last a few minutes to several hours. It effects all frequencies but is most prevalent above 100 mHz.

In some more sever cases, FM stations can travel 500 or more miles and override the local station’s transmitter site 15 miles away. In the age of digital STL’s, co-channel and adjacent channel interference can cause the STL receiver to unlock and mute. Analog STL’s will become hissy or drop out altogether. It can be a big problem.

Unfortunately, not a lot can be done about main channel interference. It will go away eventually, and no, the station causing the interference is not operating illegally or any other thing. One consolation, if the duct is open in one direction, it is also open in the other, so say hello to all your new temporary listeners in East Podunk.

As far as STL paths go, the best defense is to have a good strong signal at the receive site. Boosting the signal with a preamp at the back of the STL receiver will not do anything. Larger, higher gain antennas at the transmit and receive will help, more transmitter power will help. Sometimes diversity receive antennas will help because at the 950 frequencies 100 feet or so of altitude may make all the difference. Other than that, things like a backup RPU path using a lower frequency, a backup T-1, a backup ISDN line, a Comrex Matrix, basically anything to restore programming.

There is a tropospheric ducting prediction site called Worldwide Tropospheric Ducting Forecasts. They produce daily maps and predictions based on weather patterns.

The next propagation type known to abnormally affect VHF frequencies is called Sporadic E or E skip. This happens went ionized particles appear in the E layer of the ionosphere and it is more prevalent during the high period of the sun spot cycle when the atmosphere is unsettled due to solar storms. It is more likely to affect frequencies below 125 mHz, so main channel interference may be noted, but STL’s and other broadcast auxiliary services will not likely see any effects.

This can happen anytime of the year in any terrain and in any weather condition although it seems to be more prevalent in summer and for some unknown reason, around Christmas.

Ionospheric propagation is also known as skywave and is responsible for long distance communications in the MF (AM broadcast band) and HF (Shortwave broadcast band).

During sunlit periods, the Ionosphere breaks down into several layers; the D layer, which is responsible for absorption of AM signals during the daytime. The E layer, which normally reflects signals less than 10 MHz. The F1 and F2 layers, which primarily effect HF and lower VHF, from 10 – 40 MHz or so.

During sporadic E events, the E layer becomes heavily ionized in specific small thin areas, sometimes called clouds. This can last a few minutes or up to several hours. The effect is normally more pronounced with lower frequencies.

In this internet age, there is, of course, a website that can predict or at least define sporadic E, DXMaps.com has maps similar to the tropospheric ducting maps above.

Occasionally, solar storms will effect communications on all frequencies. The last time I heard this was in the last sun spot peak around 2000 or so. I was listening to the radio and all the stations faded for several seconds. It turns out a huge solar flare had erupted and send a stream of particles through the Earth’s atmosphere. I happened to be driving down the road and immediately my cell phone started ringing. Listening to the panicked program director on the other end, you’dve thought the earth has stopped spinning on it’s axis. Anyway, it does happen once in a while. Be Sociable, Share!

VHF Propagation Map

link: VHF Propagation Map