NVIS Notes – The Real Deal

Several real world comments on NVIS antennas from Kurt KD7JYK

Kurt popped up out of his lurkers hole to make the following comments that I totally agree upon with my comments:

  1. “NVIS is not an antenna, a frequency or a radio”

There is no special NVIS antenna as its just a dipole

NVIS usually happens below 8 Mhz when the FoF2 layer is in play as it is dependent on atmospheric conditions to work

Any HF radio can be used

2. “RF going thataway, in this case pretty much up”

If the RF signal is radiated at between 70 and 90 degrees there is a good chance it goes up and is reflected back down by the F2 layer within the regional range the resulting signal pattern effects.  Kurt explains the RF going up in a narrow beam of the bandwidth between 10 and 2 on a clock face.

3. “The more signal going up the better it becomes”

In this case we need a yagi or a beam but that itsnt practical on 80m is it? Kurt suggests a Un-beam, a partial beam or a 1/3 beam but it can simply be a wire underneath the dipole acting as a reflector.

4. Reflector Design

The reflector is 105% longer than the driven element and is optimally spaced at 1/10 of the wavelength behind the director.

For 80m its 8m high, 6m for 60m and guess what its 4m at 40m. Ok so with two poles 25 feet in length will cover 80m and shorter 16 ft Painter poles will be awesome on 60m. I suggest the reflector be about 1-2 ft off the ground to avoid ground losses.

That is totally doable for a permanent or portable NVIS set up.

5. A two band antenna

I agree with Kurt that one must have separate dipoles for each band. If a third band is needed then 3 dipoles is warranted.

6. “HMMVV Antenna Placement”

Kurt has convinced me that his theory is correct. These Humvee’s with the antenna pulled towards the front or towards the back have NOTHING TO DO with NVIS at all but are so they don’t snag power lines and electrocute the passengers and driver.

It is represented that this antenna set up is to increase low angle of radiation from a vertical to be up in the 80 degree angle to shoot up and shoot back down.

This is the way to go NVIS with a horizontal antenna just like what is used in the outback in Australia.

My adhoc skunkworks testing has proven that the mobile antenna actually works better as its horizontal than in this pulled design thus confirming that the FM 24-18 Antenna Field manual has been wrong from day one. An EZNEC study shows the vertical gain decreased from 2-15db and power down 3db at 30 degrees proving this is a poor choice of an NVIS antenna but is better than nothing I suppose.

A Vietnam RTO explained to me that in the LRRP missions NVIS was critical to get a signal above the canopy and reach the FOB and horizontal antennas on HF (PRC-74s) worked best when the PRC-25s low 1 watt and vertical antenna didnt work properly.

The PRC -74 had a 10 ft whip for short range comms and a adjustable dipole in the kit bag (doublet configuration). I have the doublet antenna and as a 44 ft version it works great on the HF bands with a tuner of course

Wouff Hong Ceremony

Wouff Hong Ceremony

The Wouff Hong Ceremony is steeped in mystery!

Don’t know what the Wouff Hong is all about? Here’s some background for ya’:

A Wouff Hong is a fictional tool used to “punish” Amateur Radio operators who demonstrate poor operating practices.

Legend has it that the Wouff Hong was invented by ARRL co-founder Hiram Percy Maxim under the pseudonym, “The Old Man,” just as radio amateurs were getting back on the air after World War One.

Early in 1919, “The Old Man” wrote in QST “I am sending you a specimen of a real live Wouff Hong . . . Keep it in the editorial sanctum where you can lay hands on it quickly in an emergency.” The “specimen of a real live Wouff Hong” was presented to a meeting of the ARRL Board and the Board voted that the Wouff Hong be framed and hung in the office of the Secretary of the League.

On display at ARRL Headquarters today, the Wouff Hong is a constant reminder to Amateur Radio operators to be mindful of their operating etiquette.

DXingh above 30 Mhz

DXing Above 30 Mhz

From The RadioReference Wiki

Remember picking up CHIPS on 42Mhz?

Talk to most people about how far a VHF signal (above 30 Mhz) will travel, and most times, the answer will be ‘line of sight’. However, as there sometimes is in nature, there’s exceptions to the rule. Many phenomenon can cause a VHF and UHF signal to travel hundreds of miles or more. Events such as a stalled weather front to a meteor shower or even the solar wind can change things in the atmosphere and make a signal travel much further than normal.

The most common type of tropospheric ducting to impact scanner hobbyists and amateur radio operators results from a low-level temperature inversion. A low-level temperature inversion is a phenomenon in which the temperature in the lower portion of the atmosphere, near the earth’s surface, is considerably cooler than a layer farther up in the atmosphere. This causes signals to be refracted thus resulting in a tunneling or ducting of the signals. Low-level temperature inversions can occur any time of the year but are often most dramatic (producing the most significant tropospheric ducting events) during the summer months. They are most often associated with surface high pressure which results in light near-surface winds allowing for radiative cooling affect. These events also commonly coincide with fog.

VHF, UHF and even 800 MHz and higher can be impacted quite significantly by these ducting events. One good example of very high frequencies being impacted is the anomalous propagation that plague the Doppler weather radar (WSR-88D) during the most extreme tropospheric ducting episodes.

Hams (and folks involved in TV/FM DXing) have been studying this for years. Many of these phenomenon have been cataloged, but not are all well understood. If you are interested in a description of how a VHF signal (or above) can travel, take a look at this article on the WikiPedia site. Keep in mind that FM and TV broadcasts, as well as ham frequencies, are found above 30 mhz. Techniques used in TV, FM and 144/220/432 Mhz DXing are applicable to DXing in the scanner bands.

Have you tried Simplex on 2M lately?

Upstate NY HAM Radio News & Information

Remember in the Toronto GTA we have the rF SuperSpreader Covid-52 net at 10am, 11am or random times


 

Posted: 19 Jan 2021 09:38 AM PST

 Simplex on 2M can be a lot of fun. If you haven’t tried it in a while, you should. You might be surprised by some of the distances you can communicate directly without a repeater.

146.52 Mhz the National 2M calling frequency is the place to start. I monitor it on a scanner and have been surprised how often you will hear someone these days. Since the Pandemic started last year, there seems to be many more folks on the air, so  give it a try. If you are using any of the digital voice modes (D-Star, Fusion, P25, NXDN), consider starting on 146.52 and then moving to an alternate frequency (like 146.535,  146.550 , 146.565 and 146.580 Mhz) out of courtesy to others who might only have analog capabilities.

Also, in Central NY there is a Simplex net held twice a month. Check it out:

CNY 2m Simplex Night – Net Control: Larry Rausch KD2MTG

1st and 3rd Thursday of every month (with exception to holidays)

146.580 Mhz Primary. 

Conceptual Local Cross Band Repeat system set up on 446.600 Mhz (NO PL) for stations to try if location / propagation presents difficulties.

Baofeng UV-5R+

Flashlight:

This is one of the best features of the radio ! Pressing a side button illuminates a very bright white LED light at the top of the radio. This is very useful for finding gear at night!

Have you ever wondered about the “Magic” of Six Meters

Have you ever wondered about the “Magic” of Six Meters? After all, you’ve probably pressed the six meter button on your rig and failed to find any magic or even any other stations. If that’s the case, you’ve identified the “tragic” of the band. But without tragic there would be no magic.

The subtitle of this book states:

AVERAGE EQUIPMENT + LIMITED ANTENNAS = EXCEPTIONAL QSOS.

It really doesn’t take much on six meters — your existing HF+6 meter rig along with a simple antenna, even a dipole, will work. In this book you’ll find out how I know that dipoles work along with how to build one of your own.

This book will also provide plenty of insight into how you, too, can “Capture the Magic of Six Meters.” It covers propagation, equipment, software, antennas, awards and contesting, as well as assistance in finding the magic.

BTW — If you’d rather read the book online along with lots of links to additional information, you can find it at 6 Meter DXing Guide – Getting Started on the Magic Band. You can also find a presentation at Six Meter Presentation @ ARRL Learning Network. Lots of ways to get this information and get on the band.

Capture the Magic of Six Meters — eBook

Capture the Magic of Six Meters —

An eBook Guide to Working the Six Meter Amateur Radio Band

Size: 13.2 MB
Version: 1.1.0
Published: 12-August-2020

HF Field Radios  and Battery Operation – Quick Notes

HF Field Radios  and Battery Operation – Quick Notes

 

All radios are classified as 12 V but are actually specified to be at 13.8 Volts.

 

If you use an SLA that is 12V then current drain and voltage drop will pull the voltage lower and they radio will turn itself off. Thus, it is better to use a Lipo or Life4 battery rated at 13.2 volts.

 

I operate a man pack RF power of 20 watts. It has lower current drain and is only about 1 S unit lower than a typical 80-100 watt station.

 

Running a HF 100 watt radio at 20 watts may still draw about 8 Amps of power due to internal circuitry optimized for high power not lower power.

 

Operating CW or 2m FM will cause the current drain to be constant where on SSB it will fluctuate with the voice wave.

 

Thus a 5-10A SLA will prove a poor choice and limit operation greatly.

 

A 10A 13.2v Bioenno battery will prove better in operating time and be lighter as well.

 

The Xiegu G90 is designed as a 20 watt radio and will draw about 4-5 Amps.

 

The Icom 705 with its 1800 MaH BP-272 battery supports operating at 10 Watts

 

BUY A PROPER LIPO OR LIFE4 BATTERY AND THROW THE SLA’S IN THE RECYLER BIN