Date   

Re: Summits on the Air (SOTA) Activation Tomorrow

Alan - W6WN
 

SOTA Activations - I had to read up whether one can use repeaters for VHF SOTA. Apparently no, but repeaters can be used to solicit SOTA simpley contacts.

http://www.k0nr.com/wordpress/2014/06/how-to-do-a-vhf-sota-activation/

Will try to break off around 4  this afternoon and listen for you.

Buena Suerte,

Alan 


Re: Summits on the Air (SOTA) Activation Tomorrow

Jef - N5JEF
 

Orion -

I've been to the top of Genoa Peak a couple times for repeater issues. I can say people won't need to be "in the area" since it can see well past 100 miles in all directions!

- Jef 

On Fri, Aug 9, 2019 at 11:37 PM Orion, AI6JB <ojendres@...> wrote:
Good Evening Everyone!

I will activate Summits on the Air (SOTA) Peak W7N/TR-007, Genoa Peak, starting tomorrow, Sat., 8/10/19, at 16:00 local time (23:00 UTC) on the National FM Calling Frequency 146.520 MHz.  Genoa Peak is on the east shore of Lake Tahoe.  If you are in that area or are looking for a challenge, please listen for me.

Hope to hear tomorrow!

73
Orion, AI6JB


Summits on the Air (SOTA) Activation Tomorrow

Orion, AI6JB
 

Good Evening Everyone!

I will activate Summits on the Air (SOTA) Peak W7N/TR-007, Genoa Peak, starting tomorrow, Sat., 8/10/19, at 16:00 local time (23:00 UTC) on the National FM Calling Frequency 146.520 MHz.  Genoa Peak is on the east shore of Lake Tahoe.  If you are in that area or are looking for a challenge, please listen for me.

Hope to hear tomorrow!

73
Orion, AI6JB


Satellite Dish

carl.wf6j@gmail.com
 



Begin forwarded message:

From: "'KA6PDY' via North Hills Radio Club" <k6is@...>
Subject: Satellite Dish
Date: August 9, 2019 at 2:42:57 PM PDT
Reply-To: KA6PDY <ka6pdy@...>


Passing this along if anyone is interested contact info below.

Fellow Hams,

I have an old 6 foot (approx 30 inch focal length) metal dish antenna my wife wants me to get rid of.  I would think that someone interested in Ham Radio microwave might be interested in this dish.  If you or if you know someone who might be interested, please contact me.  Thanks.

Don Feldman, W6GOK
Penn Valley, CA (65 miles north/east 



New job posting with Placer County Radio Services

Jef - N5JEF
 

We have a new job just now posted for a journey-level experienced radio technician/analyst.


Please pass this along to anyone you think may be qualified and interested.

- Jef


Re: The Importance (or not) of being resonant #elmer

Jef - N5JEF
 

Brian makes good comments and the paper he linked makes good sense.

Here's another paper, by Cebik, with even more detail.  If you digest this, you'll have a very good understanding.


In it, Cebik says "Hence, it is very difficult (although not impossible) to design a feedline system so that on each band we end up with just about the same impedance at the shack entry. Most amateurs let the antenna tuner do the work of transforming whatever impedance appears at the terminals to the transceiver's required 50 Ohms."

I have two of the SGC SG-230 antenna couplers, and they have been able to quickly and efficiently transform any impedance I've thrown at them.  That way, I don't spend any time calculating or cutting or trying to figure out how to route a certain length of transmission line to keep it straight down and perpendicular to the doublet (regardless of height in the field) and not too close to the ground between there and my tuner...

The SG-230s have a great reputation in marine HF, and they can often be found in good used condition on ebay for about $300.

- Jef

On Fri, Aug 9, 2019 at 1:27 PM AI6US <ai6us@...> wrote:
If your wish is to have a dipole antenna fed with ladderline and present a auto tuner with lower impedance levels (for ease of matching) across multiple bands, the feedline length should be cut at an odd multiple of 1/8th wavelength for each frequency range that you wish to work. I found that the feedline length trimming to have a significant impact on the ability for autotuners (internal 3-5:1 or external wider range autotone units) to reliably and quickly tune.

For example: on my 80m doublet, the external MFJ 993b and LDG Z11 Pro2 would not reliably tune several bands when the ladderline length was at the starting 130' length. Once I trimmed the length back to a calculated odd multiple of 1/8th (around 108') all bands reliably autotune.

To support what Jef suggests, using a manual Dentron Super Tuner, The length of the feedline or the length of radiator wires make little difference as the tuner accepts almost any mismatch value.

Here is a great document that I have found helpful in making a multiband doublet and calculating the feedline length (pages 3 and 4): 
--
Best Regards!
Brian Gohl - AI6US
(916) 770-7751


-------------------------
On Fri, 09 Aug 2019 10:24:02 -0700, Jef - N5JEF <jef@...> wrote:

On Thu, Aug 8, 2019 at 8:52 PM Alan Thompson <alan@...> wrote:

At first, I was worried about RFI in the shack using ladder line.

Coax and ladder line will both radiate if used the wrong way.

The main advantage of ladder line is its much lower loss, which can very useful with the range of SWR that goes with broadband antennas. As long as its kept balanced, it doesn't radiate.

The main advantage of coax is its convenience of routing due to its shielded design.  But it's unbalanced, so any common mode current will flow along the _outside_ of the shield and radiate, conversely, be picked up as noise in the receiver. 

But that link you sent seems to bear it out that the feed line is the biggest variable in system losses, and that ladder line is the preferred, lowest-loss choice over coax. 

They both have their place.  Coax is convenient, and works well with narrow band antennas (and it should have a balun, if you're feeding the unbalanced cable from a balanced antenna like a dipole.) 

Ladder line can be less convenient to route, but along with an antenna coupling device, it provides low-loss broad-band or multi-band operation with balanced antennas such as such as your full wave loop, or a doublet such as the double-extended-zepp. 
 

Other information I've found seems to tout ladder-line, as long as the length avoids odd multiples of a 1/4 wavelength on desitred frequencies.


There's a lot of mythology circulating about magic lengths of ladder line or coax.  Either type of transmission line can be used to transform impedance at a _single_ wavelength (plus any multiple of a half wave). This is an inherently narrow band technique, but it has been used in some cases as a compromise solution as with G5RV design, to redistribute impedance mismatches so that for certain bands they fall within the range of a limited < 3:1tuner built in to some radios.  

With a good tuner these multiples have no practical significance.

By the way, my 80 meter full-wave loop has the automatic antenna coupler (SG-230) at the antenna feed point, then a balun, then coax run underground back to the shack.

- Jef




Re: The Importance (or not) of being resonant #elmer

Brian Gohl - AI6US
 

If your wish is to have a dipole antenna fed with ladderline and present a auto tuner with lower impedance levels (for ease of matching) across multiple bands, the feedline length should be cut at an odd multiple of 1/8th wavelength for each frequency range that you wish to work. I found that the feedline length trimming to have a significant impact on the ability for autotuners (internal 3-5:1 or external wider range autotone units) to reliably and quickly tune.

For example: on my 80m doublet, the external MFJ 993b and LDG Z11 Pro2 would not reliably tune several bands when the ladderline length was at the starting 130' length. Once I trimmed the length back to a calculated odd multiple of 1/8th (around 108') all bands reliably autotune.

To support what Jef suggests, using a manual Dentron Super Tuner, The length of the feedline or the length of radiator wires make little difference as the tuner accepts almost any mismatch value.

Here is a great document that I have found helpful in making a multiband doublet and calculating the feedline length (pages 3 and 4): 
www.orarc.net/MultibandCenterfedZepp.pdf
--
Best Regards!
Brian Gohl - AI6US
(916) 770-7751


-------------------------

On Fri, 09 Aug 2019 10:24:02 -0700, Jef - N5JEF <jef@...> wrote:

On Thu, Aug 8, 2019 at 8:52 PM Alan Thompson <alan@...> wrote:

At first, I was worried about RFI in the shack using ladder line.

Coax and ladder line will both radiate if used the wrong way.

The main advantage of ladder line is its much lower loss, which can very useful with the range of SWR that goes with broadband antennas. As long as its kept balanced, it doesn't radiate.

The main advantage of coax is its convenience of routing due to its shielded design.  But it's unbalanced, so any common mode current will flow along the _outside_ of the shield and radiate, conversely, be picked up as noise in the receiver. 

But that link you sent seems to bear it out that the feed line is the biggest variable in system losses, and that ladder line is the preferred, lowest-loss choice over coax. 

They both have their place.  Coax is convenient, and works well with narrow band antennas (and it should have a balun, if you're feeding the unbalanced cable from a balanced antenna like a dipole.) 

Ladder line can be less convenient to route, but along with an antenna coupling device, it provides low-loss broad-band or multi-band operation with balanced antennas such as such as your full wave loop, or a doublet such as the double-extended-zepp. 
 

Other information I've found seems to tout ladder-line, as long as the length avoids odd multiples of a 1/4 wavelength on desitred frequencies.


There's a lot of mythology circulating about magic lengths of ladder line or coax.  Either type of transmission line can be used to transform impedance at a _single_ wavelength (plus any multiple of a half wave). This is an inherently narrow band technique, but it has been used in some cases as a compromise solution as with G5RV design, to redistribute impedance mismatches so that for certain bands they fall within the range of a limited < 3:1tuner built in to some radios.  

With a good tuner these multiples have no practical significance.

By the way, my 80 meter full-wave loop has the automatic antenna coupler (SG-230) at the antenna feed point, then a balun, then coax run underground back to the shack.

- Jef




--
Brian- AI6US


Re: The Importance (or not) of being resonant #elmer

Jef - N5JEF
 

On Thu, Aug 8, 2019 at 8:52 PM Alan Thompson <alan@...> wrote:

At first, I was worried about RFI in the shack using ladder line.

Coax and ladder line will both radiate if used the wrong way.

The main advantage of ladder line is its much lower loss, which can very useful with the range of SWR that goes with broadband antennas. As long as its kept balanced, it doesn't radiate.

The main advantage of coax is its convenience of routing due to its shielded design.  But it's unbalanced, so any common mode current will flow along the _outside_ of the shield and radiate, conversely, be picked up as noise in the receiver. 

But that link you sent seems to bear it out that the feed line is the biggest variable in system losses, and that ladder line is the preferred, lowest-loss choice over coax. 

They both have their place.  Coax is convenient, and works well with narrow band antennas (and it should have a balun, if you're feeding the unbalanced cable from a balanced antenna like a dipole.) 

Ladder line can be less convenient to route, but along with an antenna coupling device, it provides low-loss broad-band or multi-band operation with balanced antennas such as such as your full wave loop, or a doublet such as the double-extended-zepp. 
 

Other information I've found seems to tout ladder-line, as long as the length avoids odd multiples of a 1/4 wavelength on desitred frequencies.


There's a lot of mythology circulating about magic lengths of ladder line or coax.  Either type of transmission line can be used to transform impedance at a _single_ wavelength (plus any multiple of a half wave). This is an inherently narrow band technique, but it has been used in some cases as a compromise solution as with G5RV design, to redistribute impedance mismatches so that for certain bands they fall within the range of a limited < 3:1tuner built in to some radios.  

With a good tuner these multiples have no practical significance.

By the way, my 80 meter full-wave loop has the automatic antenna coupler (SG-230) at the antenna feed point, then a balun, then coax run underground back to the shack.

- Jef


Re: The Importance (or not) of being resonant #elmer

Alan - W6WN
 

Thanks again for the insight. That's pretty close to what I've run into. I have it on my list to plot my loop to see what it's really doing but, for now, it just seems to work really well, and it was cheap!

At first, I was worried about RFI in the shack using ladder line. But that link you sent seems to bear it out that the feed line is the biggest variable in system losses, and that ladder line is the preferred, lowest-loss choice over coax. 

Other information I've found seems to tout ladder-line, as long as the length avoids odd multiples of a 1/4 wavelength on desitred frequencies.
.
Best Regards,

Alan -  W6WN


Re: The Importance (or not) of being resonant #elmer

Jef - N5JEF
 

Alan -

Your full wave loop ought to do a good job for NVIS on 160, being at just about the lower limit for effective height at 1/8 wavelength.
Then at 80 meters it should be good in all directions, but with a quite low takeoff angle, so very good for 80 meter DX but not so good for local/regional.
Then at 40 meters, it'll split into a clover leaf, with higher gain for great DX in some directions, and not much at all in others.

I have an 80 meter full-wave loop here at about 30 ft.  Very happy with it on 80 and 40 for solid coverage of the west coast.
I need to get back to work on my 10 ft diameter loop...

- Jef






On Thu, Aug 8, 2019 at 7:06 PM Alan Thompson <alan@...> wrote:
Great read - Food for thought.

I put up a closed-loop antenna cut to a full wavelength at 160 meters and off the ground about 60'. I feed it with a piece of 450 ohm ladder lane that runs all the way into an ATU that sits on my desk. I can confirm that I've been able to work 160, 80, 40 and DX on 20 meters into the south Pacific and the Ukraine with 100 watts fed into this setup. Haven't modeled it, and no doubt the radiation patterns are wonky across the bands, but it can and does work.

Best Regards,

Alan Thompson -  W6WN


Re: The Importance (or not) of being resonant #elmer

Alan - W6WN
 

Great read - Food for thought.

I put up a closed-loop antenna cut to a full wavelength at 160 meters and off the ground about 60'. I feed it with a piece of 450 ohm ladder lane that runs all the way into an ATU that sits on my desk. I can confirm that I've been able to work 160, 80, 40 and DX on 20 meters into the south Pacific and the Ukraine with 100 watts fed into this setup. Haven't modeled it, and no doubt the radiation patterns are wonky across the bands, but it can and does work.

Best Regards,

Alan Thompson -  W6WN


Upcoming Event: SFARC Board Meeting - Fri, 08/09/2019 6:00pm-7:00pm #cal-reminder

sfarc@w6ek.groups.io Calendar <sfarc@...>
 

Reminder: SFARC Board Meeting

When: Friday, 9 August 2019, 6:00pm to 7:00pm, (GMT-07:00) America/Los Angeles

Where:Mel's Diner, 1730 Grass Valley Hwy, Auburn

View Event

Description: Monthly SFARC Board meeting. The venue may change from time to time ... Inquire on the repeater or www.W6EK.org for updates


The Importance (or not) of being resonant #elmer

Jef - N5JEF
 

I've had a couple people from this list contact me directly, asking how I can say that SWR and resonance have nothing to do with the efficiency of an antenna, when they hear almost everybody in the ham world talking about how important it is to trim you antenna to resonance, and get the lowest possible SWR to know that your antenna is radiating efficiently.

I came across this article that explains it quite clearly:

FYI,

- Jef  N5JEF


Upcoming Event: General Meeting - Fri, 08/09/2019 7:30pm-9:30pm #cal-reminder

sfarc@w6ek.groups.io Calendar <sfarc@...>
 

Reminder: General Meeting

When: Friday, 9 August 2019, 7:30pm to 9:30pm, (GMT-07:00) America/Los Angeles

Where:1225 Lincoln Way, Auburn, CA - City Hall, Rose Room

View Event

Description: Come a little early and visit! Ample parking in back of the building. See map at http://www.w6ek.org for details (Hwy49 & Lincoln Way)


Upcoming Event: SFARC Net - Thu, 08/08/2019 7:30pm-8:30pm #cal-reminder

sfarc@w6ek.groups.io Calendar <sfarc@...>
 

Reminder: SFARC Net

When: Thursday, 8 August 2019, 7:30pm to 8:30pm, (GMT-07:00) America/Los Angeles

Where:W6EK Repeater - 145.430 -600, PL162.2

View Event

Description: Check-in for Club updates from Officers and members, QSTs and more. Everyone is welcome!


Upcoming Event: Elmer Net - Wed, 08/07/2019 7:30pm-8:30pm #cal-reminder

sfarc@w6ek.groups.io Calendar <sfarc@...>
 

Reminder: Elmer Net

When: Wednesday, 7 August 2019, 7:30pm to 8:30pm, (GMT-07:00) America/Los Angeles

Where:W6EK Repeater - 145.430 -600, PL162.2

View Event

Description:

This is our every other weekly net devoted to answering questions, providing answers and scheduling help for all Hams. No question is "stupid". We encourage everyone to ask away so we can all learn and grow more knowledgeably together. Web address: http://w6ek.org/nets.html


Re: HT Counterpoise - "Tiger Tails"

Jef - N5JEF
 

Yup.  The 1-1/4 wavelength doublet is often known as a double-extended zepp.  It's my favorite antenna for camping with HF, and the one I used at the last Boy Scout JOTA. But it is long.  Since each leg is 5/8 wavelength, that makes it about 166 feet at 40 meters. The phasing of the the two sections provides about 3dB compared to a dipole on 40 meters, and on 75 meters it radiates like a half-wave dipole but the feedpoint impedance is quite different.  On 60 meters it radiates more like a full-wave doublet, with high impedance.  Due to the various impedance mismatches, I use about 35 feet of 450-ohm window line from the feedpoint down to an automatic matching unit on the ground (yes, that transforms the impedance again, but it doesn't matter due to the low loss of the balanced transmission line.)  In my opinion, this provides about the best 75-60-40 meter NVIS antenna practical if the center is roughly 35 ft above the ground. 

Then, if you want to play DX, you can use this antenna at higher and higher frequencies and it will produce quite high gain in specific directions that get closer to the axis of the antenna wire with shorter wavelengths.  If you wanted to take the time, you could orient the wire to optimize for 20 meters in particular directions.  These lobes and nulls get hard to predict in the field though, and I spend nearly all my time on NVIS so I don't worry about it.

Since we're on the subject of antenna designs, here's an inverted V that minimizes feedline loss:

image.png





On Mon, Aug 5, 2019 at 10:05 AM <ojendres@...> wrote:

Jef,

 

Thanks for taking the time to put this together!  I certainly learned something, like a 1-1/4 wavelength doublet has 3 db gain over a half wave dipole.

 

73

Orion Endres, AI6JB

1201 Wood Oak Court, Roseville, CA 95747-7383

(916) 788-8251 H \\ (916) 534-8251 C

 

What the heck does “73” mean?  73 is morse code short hand for “Best Regards” used by Ham radio operators.  It’s origin goes all the way back to the landline telegraph days.

 

 

 

From: sfarc@w6ek.groups.io <sfarc@w6ek.groups.io> On Behalf Of Jef - N5JEF
Sent: Sunday, August 04, 2019 14:10
To: sfarc@w6ek.groups.io; alan@...
Subject: Re: [from W6EK Groups.io] HT Counterpoise - "Tiger Tails"

 

It's nice to see someone taking the time to make measurements, but there are several serious inaccuracies in this article.  Too bad the testing was not carried out as scientifically as that other recent example of antenna testing, forwarded by Jim N6MED.

 

"As most of us know, a transmitted signal works best with a resonant antenna specific to that frequency. 

"A resonant antenna typically means the best radiation pattern off the antenna and a low SWR (among other things, I will not go into too much detail)." 

 

Simply not true, and misleading, but a very common example of ham lore.

 

For an antenna to be resonant simply means that it is at a length where the inductive and capacitive reactance cancel each other.  Multiples of a quarter wave will be resonant, but can have hugely different impedance (thus SWR) and radiation pattern.  A quarter-wave monopole such as is common for VHF on the roof of a vehicle, when resonant, will have a feed-point impedance impedance of around 37-ohms.  This, matched to a 50-ohm feedline, means you will always have some reflected power and never achieve an actual 1:1 SWR.  A half-wave dipole in free space has a feedpoint impedance of about 73-ohms, so again, you never have a 1:1 SWR, although bringing the dipole closer to earth will lower it's impedance and bring it closer to 1:1 SWR, while also distorting its radiation pattern.  The popular 5/8 wave mobile whip is not resonant at all, but it can sometimes provide advantages over a 1/4-wave resonant whip due to its additional length, and by getting the region of maximum antenna current higher above the vehicle.  The popular double-extended Zep (a 1 1/4 wave doublet) has the most lateral gain of any doublet, but it is certainly not resonant.  

 

Resonance and SWR have absolutely nothing directly to do with antenna radiation pattern or radiation efficiency, but are important in terms of feedline loss and matching to the radio equipment.

 

Antenna efficiency is simply the ratio of power applied / power lost as heat.  It has nothing to do with SWR, resonance, or antenna pattern.  This is why a small 1/10 wavelength loop antenna can approach the same efficiency as a full size dipole if the conducting surface is sufficient to minimize loss by heating.  Power radiated is proportional to the movement of charge times the lineal distance of the movement.  

 

Antenna pattern has to do with the geometry of the antenna and the field(s) produced.  A half-wave dipole is the simplest, but the a 1 1/4 wave doublet has 3dB more gain (and needs impedance matching.)  Any wire longer than about 1 1/4 wave begins to produce lobes and nulls, that increasingly direct more energy along the axis of the antenna.  Longer is not necessarily better when it comes to antennas.

 

The height of an antenna above ground can have huge effect on the radiation pattern due to constructive or destructive interference with the ground.

 

And so on...

 

"it is not possible to have a full quarter (over 19 inches) or half wave (19 inches times two) with a handheld that is only approximately 4 inches tall itself."

 

It certainly is possible at VHF, but not always practical, as shown recently in the video forwarded by Jim.  And a full quarter wave at UHF is the norm.

 

You know, I was going to take the time to comment on a few other blatant misconceptions in the article, but I feel that the amount of time to do so probably outweighs anyone's interest in the subject.

 

Let me just cut to the chase here and point out that he had both transmitter and receiver well within the near field (only 11 feet apart) and he did not account in any way for height or reflections.  I'm sure he saw widely varying numbers--both positive and negative--but he did not even mention them, and reported only the positive.

 

If anyone cares, take a look at the video Jim linked to and the excellent theoretical and practical concerns that we accounted for there.

 

This is the kind of well-meaning crap that gives amateurs a bad reputation among professionals.

 

I care--a lot--because I think there is an important role for amateurs in emergency preparedness and advancing the state of the art in areas that might be overlooked by more commercial interests, but sheesh, there is far more baloney than thoughtful, informed knowledge getting put out and regurgitated.

 

- Jef N5JEF

 

 

 

 

 

On Sun, Aug 4, 2019 at 10:02 AM Alan Thompson <alan@...> wrote:

I remembered seeing that someone had done some testing on the effects of Tiget Tails but could not locate it until now:

http://www.km4fmk.com/blog/counterpoise.html

Best Regards,

Alan Thompson -  W6WN


Re: HT Counterpoise - "Tiger Tails"

Orion, AI6JB
 

Jef,

 

Thanks for taking the time to put this together!  I certainly learned something, like a 1-1/4 wavelength doublet has 3 db gain over a half wave dipole.

 

73

Orion Endres, AI6JB

1201 Wood Oak Court, Roseville, CA 95747-7383

(916) 788-8251 H \\ (916) 534-8251 C

 

What the heck does “73” mean?  73 is morse code short hand for “Best Regards” used by Ham radio operators.  It’s origin goes all the way back to the landline telegraph days.

 

 

 

From: sfarc@w6ek.groups.io <sfarc@w6ek.groups.io> On Behalf Of Jef - N5JEF
Sent: Sunday, August 04, 2019 14:10
To: sfarc@w6ek.groups.io; alan@...
Subject: Re: [from W6EK Groups.io] HT Counterpoise - "Tiger Tails"

 

It's nice to see someone taking the time to make measurements, but there are several serious inaccuracies in this article.  Too bad the testing was not carried out as scientifically as that other recent example of antenna testing, forwarded by Jim N6MED.

 

"As most of us know, a transmitted signal works best with a resonant antenna specific to that frequency. 

"A resonant antenna typically means the best radiation pattern off the antenna and a low SWR (among other things, I will not go into too much detail)." 

 

Simply not true, and misleading, but a very common example of ham lore.

 

For an antenna to be resonant simply means that it is at a length where the inductive and capacitive reactance cancel each other.  Multiples of a quarter wave will be resonant, but can have hugely different impedance (thus SWR) and radiation pattern.  A quarter-wave monopole such as is common for VHF on the roof of a vehicle, when resonant, will have a feed-point impedance impedance of around 37-ohms.  This, matched to a 50-ohm feedline, means you will always have some reflected power and never achieve an actual 1:1 SWR.  A half-wave dipole in free space has a feedpoint impedance of about 73-ohms, so again, you never have a 1:1 SWR, although bringing the dipole closer to earth will lower it's impedance and bring it closer to 1:1 SWR, while also distorting its radiation pattern.  The popular 5/8 wave mobile whip is not resonant at all, but it can sometimes provide advantages over a 1/4-wave resonant whip due to its additional length, and by getting the region of maximum antenna current higher above the vehicle.  The popular double-extended Zep (a 1 1/4 wave doublet) has the most lateral gain of any doublet, but it is certainly not resonant.  

 

Resonance and SWR have absolutely nothing directly to do with antenna radiation pattern or radiation efficiency, but are important in terms of feedline loss and matching to the radio equipment.

 

Antenna efficiency is simply the ratio of power applied / power lost as heat.  It has nothing to do with SWR, resonance, or antenna pattern.  This is why a small 1/10 wavelength loop antenna can approach the same efficiency as a full size dipole if the conducting surface is sufficient to minimize loss by heating.  Power radiated is proportional to the movement of charge times the lineal distance of the movement.  

 

Antenna pattern has to do with the geometry of the antenna and the field(s) produced.  A half-wave dipole is the simplest, but the a 1 1/4 wave doublet has 3dB more gain (and needs impedance matching.)  Any wire longer than about 1 1/4 wave begins to produce lobes and nulls, that increasingly direct more energy along the axis of the antenna.  Longer is not necessarily better when it comes to antennas.

 

The height of an antenna above ground can have huge effect on the radiation pattern due to constructive or destructive interference with the ground.

 

And so on...

 

"it is not possible to have a full quarter (over 19 inches) or half wave (19 inches times two) with a handheld that is only approximately 4 inches tall itself."

 

It certainly is possible at VHF, but not always practical, as shown recently in the video forwarded by Jim.  And a full quarter wave at UHF is the norm.

 

You know, I was going to take the time to comment on a few other blatant misconceptions in the article, but I feel that the amount of time to do so probably outweighs anyone's interest in the subject.

 

Let me just cut to the chase here and point out that he had both transmitter and receiver well within the near field (only 11 feet apart) and he did not account in any way for height or reflections.  I'm sure he saw widely varying numbers--both positive and negative--but he did not even mention them, and reported only the positive.

 

If anyone cares, take a look at the video Jim linked to and the excellent theoretical and practical concerns that we accounted for there.

 

This is the kind of well-meaning crap that gives amateurs a bad reputation among professionals.

 

I care--a lot--because I think there is an important role for amateurs in emergency preparedness and advancing the state of the art in areas that might be overlooked by more commercial interests, but sheesh, there is far more baloney than thoughtful, informed knowledge getting put out and regurgitated.

 

- Jef N5JEF

 

 

 

 

 

On Sun, Aug 4, 2019 at 10:02 AM Alan Thompson <alan@...> wrote:

I remembered seeing that someone had done some testing on the effects of Tiget Tails but could not locate it until now:

http://www.km4fmk.com/blog/counterpoise.html

Best Regards,

Alan Thompson -  W6WN


Re: HT Counterpoise - "Tiger Tails"

Jef - N5JEF
 

Alan -

You're welcome.  I hope it helps a little in getting people to look at actual science and engineering in favor of all this anecdotal "evidence."

And I sincerely appreciate his trying the experiment and passing it along.  

If I were talking directly to him, I would have tried to kindly point out that you can't measure an antenna's far field properties when you're in the near field, and by the way, did you notice all those crazy reflections while you were moving things around...?

- Jef

On Sun, Aug 4, 2019 at 2:19 PM Alan Thompson <alan@...> wrote:
Jef,

Thank you for the insight.

Much appreciated.

Alan


Re: HT Counterpoise - "Tiger Tails"

Alan - W6WN
 

Jef,

Thank you for the insight.

Much appreciated.

Alan