80 Meter Driven Array

[W1IA]

It is up and has been a fun night! The intial testing for the antenna was great.

Info: 2 elements cut for 3800 kHz spaced at 55 feet up 65-70 feet. Fed each with 3 half waves into shack and 115 degree phase delay in one element.

Over the pond was a typical 3-4 dB with an average of 15-20 dB front to back.

The input impedance is around 18 ohms with an X = 16 @ 3800 kHz

I used my trusty Johnson Matchbox to match the input impedance to use for 250 watts. Today I hope to finish the front/back switching etc.. Along with the phasing box to change delay line from 90 to 135 degrees.

Brent W1IA 

[K9ACT]

Guess I didn't make my question clear last night or condx garbled it but....

When pointed at us, you were nominally the same as the dipole.  When pointed across the pond, you were barely readable and about 15 db below the dipole.

I understand why getting rid of the backside noise is good but I do not understand why it is not 15 db above the dipole when pointed this way.

Jack

[Steve - WB3HUZ]

15 db above the dipole

Because the array has nowhere near 15 dB of forward gain. You should see 3-5 dB over the dipole under perfect conditions. With fading, antenna placement, propagation modes, you may not be able to tell any difference.

Congrats on getting the array up and working Brent. Hope to hear it on the air tonight. I'll have to work harder now to strap you in the DX Window, when working mobiles in Moscow with XYLs named Svetlana.

[WA1GFZ]

very cool Brent.
The performance sounds the same as my set up worked. I was just out in the woods today looking at the tree that will not release my north element.
I think I may saw it down and put the ant back up.
Now consider this. Add another 42 feet of 50 ohm line to each run. This will raise the Z. Then do the splitter with with 70 ohm cable.
I found an odd multiple of a quarter wave for the feed line worked better. Actually I tuned the length for best VSWR with series stubs.
fc

[N3DRB The Derb]

Jack,

thats a serious scope in your avatar. I have begun collecting  small Japanese made refractors from the 50's and 60's for fun. Towas, Sears, etc.

Derb

[K9ACT]

Jack,

thats a serious scope in your avatar. I have begun collecting  small Japanese made refractors from the 50's and 60's for fun. Towas, Sears, etc.

Derb

You might get a honk out of the picture I took of The Great Globular Cluster in Hercules with a dept store Tasco http://schmidling.com/tasco.htm

The point of this exercise was to demonstrate that one's money is far better spent on a good mechanical mount then on glitzy expensive telescopes.

Having said that, a quality scope helps also  http://schmidling.com/m13.htm

js

[Steve - WB3HUZ]

The point of this exercise was to demonstrate that one's money is far better spent on a good mechanical mount then on glitzy expensive telescopes.

Most especially when taking time lapse photos. The inexpensive CCDs have revolutionized amateur astronomy, although I see you used film in some of your shots. Cool.

[Todd, KA1KAQ]

I have a 4.5" Newtonian Reflector, 450x. Haven't used it in years. Makes those moon craters look like swimming pools, but Jupiter and its moons are fuzzy due to marginal optics.

Brent, condx were poor last night, but for what it's worth: when you were on the array I could barely tell you were in there. On the dipole, I could at least hear you and make out about 50% of what you were saying. So it would appear to be working? 

 

[K9ACT]

Most especially when taking time lapse photos. The inexpensive CCDs have revolutionized amateur astronomy, although I see you used film in some of your shots. Cool.

Actually, the inexpensive CCD's are just about  useless for time exposures as the noise buildup precludes exposures longer than a few seconds.  The CCD cameras used for astro imaging use Peltier devices to cool the chip and all sorts of other tricks to minimize noise.

I started doing this long before they existed and film was all there was.  Film is still the only option for large format but even that will soon be history as Kodak quit producing  TechPan which was the only film really suited to astrophotography.

Not only is electronic superior in every other respect but combined with computers and software, we (amateurs) routinely take hundreds of images, sort out the best, stack, average and process them for detail impossible to get with the largest professional scopes available only a few decades ago.

CCD was clearly a revolution is astronomy.

js

[K9ACT]

I have a 4.5" Newtonian Reflector, 450x. Haven't used it in years. Makes those moon craters look like swimming pools, but Jupiter and its moons are fuzzy due to marginal optics.
 

As a point of interest, under perfect conditions and with perfect optics, the maximum resolution possible with a telescope is 50 x the aperture in inches.  This would be 225 for your 4.5" Newt.  The 450x eyepiece is Madison Ave stuff.  It is useless.  In the real world, 25 x A is more realizable.

There are two reasons why bigger is better in scope.  One is this resolving power issue and the other is light gathering power which relates to what you get with a given exposure time or what is visually visible.

js

[Steve - WB3HUZ]

Actually, the inexpensive CCD's are just about  useless for time exposures as the noise buildup precludes exposures longer than a few seconds.  The CCD cameras used for astro imaging use Peltier devices to cool the chip and all sorts of other tricks to minimize noise.

For sure. When I say inexpensive, it's relative to the cost of prior generation electronic cameras and/or film. If amateur astronomers can afford something, it's inexpensive by definition.

I've been doing the stacking and averaging of images since the early 80's.

[K9ACT]

Actually, the inexpensive CCD's are just about  useless for time exposures as the noise buildup precludes exposures longer than a few seconds.  The CCD cameras used for astro imaging use Peltier devices to cool the chip and all sorts of other tricks to minimize noise.

I've been doing the stacking and averaging of images since the early 80's.

People were doing that with film back then but that was over my pay grade or patience.

What is really cool is that during the most recent Mars apparition, people were using $50 web cams to capture video streams and running this through automatic sorting programs which found the best of thousands then stacked and averaged them. 

They produced some very impressive pics.  I evaluated this myself but concluded that I could do better with fewer better pics with a real camera.  Check out my Mars pages.

Unfortunately, aside from Mars then, Jupiter and the Moon, you quickly run out of light for web cams and are stuck with time exposures and back to cooled CCD's.

js

[K6JEK]

It is up and has been a fun night! The intial testing for the antenna was great.

Info: 2 elements cut for 3800 kHz spaced at 55 feet up 65-70 feet. Fed each with 3 half waves into shack and 115 degree phase delay in one element.

Over the pond was a typical 3-4 dB with an average of 15-20 dB front to back.

The input impedance is around 18 ohms with an X = 16 @ 3800 kHz

I used my trusty Johnson Matchbox to match the input impedance to use for 250 watts. Today I hope to finish the front/back switching etc.. Along with the phasing box to change delay line from 90 to 135 degrees.

Brent W1IA 

Brent, I would think you could get 6 dBd gain.   I'm using something similar except, unfortunately much lower. Modeling showed 6dBd, if I recall correctly.   I wrote this thing up for Electric Radio a couple of months ago.   You'd think I could remember!@#

I can find the modeling if you want it.   I'm quite fond of the antenna.   

[Steve - WB3HUZ]

People were doing that with film back then but that was over my pay grade or patience.

Wow. I would imagine so. Sounds painful. What I was doing was electronic.

[pe1mph]

Sent you the recording Brent!

Greetings,

Henk

[W1IA]

It is up and has been a fun night! The intial testing for the antenna was great.

Info: 2 elements cut for 3800 kHz spaced at 55 feet up 65-70 feet. Fed each with 3 half waves into shack and 115 degree phase delay in one element.

Over the pond was a typical 3-4 dB with an average of 15-20 dB front to back.

The input impedance is around 18 ohms with an X = 16 @ 3800 kHz

I used my trusty Johnson Matchbox to match the input impedance to use for 250 watts. Today I hope to finish the front/back switching etc.. Along with the phasing box to change delay line from 90 to 135 degrees.

Brent W1IA 

Brent, I would think you could get 6 dBd gain.   I'm using something similar except, unfortunately much lower. Modeling showed 6dBd, if I recall correctly.   I wrote this thing up for Electric Radio a couple of months ago.   You'd think I could remember!@#

I can find the modeling if you want it.   I'm quite fond of the antenna.   

Please send the model data Jon..Thanks

You guys hijacked my thread HA!

Brent W1IA

[W1IA]

Sent you the recording Brent!

Greetings,

Henk

Thanks Henk...very soon we will have a QSO

73 Brent W1IA

[K9ACT]

You guys hijacked my thread HA!

Brent W1IA

I forgot to ask at the end of my last.... "where is Brent?" but forgot.

You also forgot to answer my original question which was something like.... why doesn't the forward gain mirror the backward loss?

js

[Steve - WB3HUZ]

That was answered early on.

http://amfone.net/Amforum/index.php?topic=12589.msg92741#msg92741

You guys hijacked my thread HA!

Brent W1IA

I forgot to ask at the end of my last.... "where is Brent?" but forgot.

You also forgot to answer my original question which was something like.... why doesn't the forward gain mirror the backward loss?

js

[WU2D]

Brent - Verticals Rock for DX on 80.

I worked a few of the Czech CW stations in that OK contest last night on my wireless set 19 with 10 Watts out. Needless to say, that radio does not make the premium list!

It all about the antenna. This was on my three element vertical (ground plane) Yagi.
Since last year I added a third element and plane director.

Mike WU2D 

[ve6pg]

...tina.....rockin' into my qth....tim...sk..

[KA1ZGC]

Heard you talking with Don KYV and someone in 5-land last night when you were doing the A/B tests last night.

("...this is the shaded dipole, this is the wire array...")

You were audibly stonger here on the array, but I was away from the meter.

Congrats!

--Thom
King Abraham One Zebraham George Charlie

[WA1GFZ]

Brent one thing I wanted to try but never got around to it was instead of making the feedline an odd quarter wave go even and make the last quarter wave 35 ohm coax rather than 50 ohm to get the low Z closer to 50 ohms for each antenna. I was going to make 35 ohm coax by putting two quater wave sections of 70 ohm in parallel. It would have taken 4 quarter wave sections to do both dipoles. Then I thought the best place to do this was right off the antenna to jace the Z to 50 ohms at the input of the feed line run.
Tom Vu built BB transformers at each feed point. That works also but you have to support the center when you have all that iron in the air. gfz

[WU2D]

Don,

You were loud up here in NH late last night. I was playing with my homebrew Regen listening to some CW and I tuned up the band  and bang - and you captured it- full phase lock. I did not have the minidisc hooked up or I would have some audio.

Mike WU2D

[W1IA]

Heard you talking with Don KYV and someone in 5-land last night when you were doing the A/B tests last night.

("...this is the shaded dipole, this is the wire array...")

You were audibly stonger here on the array, but I was away from the meter.

Congrats!

--Thom
King Abraham One Zebraham George Charlie

Tom,
I heard you in the back ground with the CW..HA!
You should have fired up.

Brent