Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
antenna height.....




 
The AM Forum
April 14, 2021, 03:10:07 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 [2]   Go Down
  Print  
Author Topic: antenna height.....  (Read 12356 times)
0 Members and 1 Guest are viewing this topic.
Steve - WB3HUZ
Guest
« Reply #25 on: October 30, 2009, 05:16:05 PM »

Quote
I dont have the room for Directional antennas on the low bands.  I am pretty much maxed out with my Zep.  One can dream though.

Check out the K9AY. It does not take much space. I bet you could fit one in your yard. They are easy to build and I've used one since 2006 (wish I had built one sooner). My Beverage is better but for the space required, the K9AY is hard to beat.

And yes, you can null out local noises.



Quote
All I can figure is that the Yagi's vertical pattern off the rear is fairly broad - while the phased antennas are a sharp null, thus unstable.

That's exactly it. It's not geometric F/B but the entire back side of the pattern. Those are the best antennas to reduce noise/static.
Logged
K5UJ
Contributing
Member
*
Offline Offline

Posts: 2845



WWW
« Reply #26 on: October 30, 2009, 05:53:31 PM »

can't null out t-storms because lightning strikes are always at random distances and directions so the phase relationship is always changing. 

I have found the only thing that works with them is high power carrier, and good antenna, not at your QTH but at the station you're working.  Then all you have to do is turn down the RF gain.  Smiley

This works great with 50 KW broadcast stations laying down a blanketing groundwave from a 190 degree tower, which squelches storm static into punyness within a certain field strength contour, but hams are much more power challenged  Embarrassed

Rob
Logged

"Not taking crap or giving it is a pretty good lifestyle."--Frank
Jim, W5JO
Member

Offline Offline

Posts: 2474


« Reply #27 on: October 30, 2009, 05:58:47 PM »

What Rob said and also what HUZ said about the K9AY.  I played with one and you really will like it.  The only problem with buying the box and controller is the price.  It does do a very good job if installed over radials.
Logged
Steve - WB3HUZ
Guest
« Reply #28 on: October 30, 2009, 07:07:02 PM »

There are other small options too. As Jim mentioned, a small "shielded" loop can put nulls and T-storms at certain distances.

Also, don't think that the stations need to be DX or similar for the K9AY or a Beverage to be useful. I see nice SNR improvements on stations less than 300 miles away on both the K9AY and the Beverages. I'll post some audio clips later.
Logged
Steve - WB3HUZ
Guest
« Reply #29 on: October 30, 2009, 08:32:28 PM »

Here are some audio clips. The first is of Kerri - KC2UFU on 3872 kHz the other night. She is located 211 miles from me. The static is not terrible but you can hear the noise drop when I switch from the dipole to the Beverage. The clip starts out on the dipole, then switches to the Beverage at about 12 seconds, then back to the dipole at 27 seconds and then back to the Beverage at 32 seconds.

The second clip has Kerri and Bob - K1KBW. Bob is located 352 miles from me. Here you can hear the reduction of some SSB QRM. Both Kerri and Bob are located Northeast of me, right in the main lobe of my Beverage. The SSB stations were all to the South of me. Some were in Florida. Notice the drop off in the SSB when switching from the dipole to the Beverage at 8 seconds. Then the SSB comes back up at 22 seconds when I switch back to the dipole and drops again at 30 seconds when I switch to the Beverage. Then it's back to the dipole at 44 seconds and back to the Beverage at 52 seconds. The drop off in the SSB is completely due to the back and side rejection of the Beverage. I'm not changing IF bandwidths at all.

* kc2ufu29oct090255z3872.mp3 (796.64 KB - downloaded 236 times.)
* k1kbwkc2ufu29oct090252z3872.mp3 (988.46 KB - downloaded 229 times.)
Logged
WU2D
Contributing
Member
*
Offline Offline

Posts: 1769


CW is just a narrower version of AM


« Reply #30 on: October 30, 2009, 09:01:35 PM »

I have a tuned loop on the back deck for 80M. It is a 4 ft diameter loop of coax  with a split shield and resonated with a variable at the feed with a split C match. I am having issues matching it efficiently to 50 Ohms. The beverage is kicking it around the block for signal strength.

I am sure that this antenna will work better once I figure out how to match it.

With broadcast loops I have used a few unshielded turns of hookup wire around  a similar form tuned with a cap and a Faraday loop of about 1 ft in diameter directly feeding the coax roughly in the center and this works great for sensitivity and it has a sharp null.

Mike WU2D
Logged

These are the good old days of AM
KC2UFU
Guest
« Reply #31 on: December 02, 2009, 09:24:58 PM »

Hey Steve I don't sound half bad with my 35 watts carrier power.  I guess if everyone had your antenna setup I wouldn't have to burn my fingers building this amp!

Now I know what I sound like, thanks!
Logged
VE3GZB
Member

Offline Offline

Posts: 564


« Reply #32 on: December 02, 2009, 09:34:56 PM »

I used to SWL in a basement apartment many years ago. I'd get great reception from a piece of wire strung across the ceiling!

Most of us know how the height of an antenna (dipole in this case) affects the performance but Im wondering what is the affect on  the receiving performance and can this be plotted.
Thanks,


Bill
Logged
flintstone mop
Contributing
Member
*
Offline Offline

Posts: 5032


« Reply #33 on: December 05, 2009, 09:16:05 AM »

This info here is telling me that I'll have to sharpen my skills for receiving, if we move to the Philippines.
I think I understand why they (especially  Europeans ) use mag loop antennas. Antenna space is limited and the tropical location will get pretty noisy from MaNature. Noise cancelling will work somewhat, but like Tom says, a crap shoot.


Fred
Logged

Fred KC4MOP
Pages: 1 [2]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.077 seconds with 19 queries.