Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: 4-BTV Flagpole  (Read 14928 times)
KC9RAK
Member

Posts: 22




Ignore
« Reply #15 on: May 30, 2012, 09:32:52 PM »

Well I filled out the architectural forms and submitted them to the HOA and now I wait for somone to give me permission to put up a flagpole.  I mentioned to my wife how this was a pain and she simply said 'Well let's move out to the country'.  I hadn't even considered it but it seems we were both thinking the same thing.  We built this current house 14 years ago about 11 years before I had any desire to get into Ham radio.  I don't have any ill feelings toward the HOA or the covenants.  I agreed to them when we built and understand the purpose they serve.  But we both now feel a move is in order for various reasons.

So now she's found a place about 10 miles away that has 8+ acres that may solve all of my compromise stealth antenna ideas.  So now we have the arduous task of getting this place ready to sell and do the whole sell a house / buy a house dance.  Will be worth it in the end though.  Will keep you posted!!

Dave
Logged
W5DQ
Member

Posts: 1209


WWW

Ignore
« Reply #16 on: May 31, 2012, 02:42:54 PM »


To avoid tuning it up - adjusting the lengths of the sections - you can set the dimensions per the BTV assembly manual and touch up the match at the shack using a tuner.


If at all possible, I would try to tune the sections to get them within the ballpark of being resonant and avoid the possibility of any high SWR on the feedline with the associated losses. Sure it may take a little while and maybe if you're really lucky, the pre-set measurements will get you close enough. If you're just going to use a tuner to tune the antenna, why bother using a trapped vertical and having trap losses for nothing. Just put up a non-resonant vertical tube like a 43' ft type. I think S9 has shorter versions that might work in your situation since 43' is a bit tall for a run of the mill flag pole Smiley

I have read these stories about folks just throwing up a vertical using only a ground rod of some length without any radials and all I can say is they must be very lucky to have extremely good soil type that is conducive to using a vertical. My QTH here in the desert does not and I have to use radials or it's a waste of time to use the 6BTV. I suggest you read the info on the DX Engineering website to learn about the effect of ground losses without using a set of PROPER radials. You might be surprised on the results on using and not using them.

As it all depends on your soil type. I have a 6BTV installed over dry, desert soil (mostly alkali type dirt and sand mixed) and without a set of decent length radials, my 6BTV install would not even start to tune up anywhere near the pre-sets. After I added 40 radials of 30-60 ft each on average (have about 10-12 that are less than 20 ft long close to the wooden fence and a dozen or so around 60 ft to help on 160M/80M), the SWR is below 1.5:1 on all bands and the antenna is a real performer now.

Just my input from a real world 6BTV user. Good Luck on the flagpole project.

Gene W5DQ
Logged

Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
K3VAT
Member

Posts: 704




Ignore
« Reply #17 on: June 01, 2012, 04:59:42 AM »

A Navy friend of mine put up a 24 foot flag pole antenna ... He has a pretty small yard in Navy housing...I think his back yard is around 20 feet wide by 40 feet long so not that big at all but what he DOES have is a great ground plane. He has 100 ten foot radials and another 40 or so that are 20 feet long and bent here and there to fit. I might do something similar here in Japan when my JA license arrives.  Lane, Ku7i

Hi Lane,
Hope that you get that JA licence soon.  Band condx are pretty good nowadays.
A couple items in your post regarding your friends antenna (described above): 100 ten-foot radials are a waste of wire - return current saturation for 10M thru 40M with 10 foot radials takes place using ~ couple of dozen radials (Dave, WX7G may be able to provide a more exact number).  Bent radials are not an effective radial; just run your wire out as far as you can in a straight line.  Once you get close to erecting your vertical antenna, let us know the distances to the property perimeter from the antenna, what bands are of interest to you, and whether you're interested in DX'ing, 'local' contacts, or what and someone should be able to provide you with solid recommendations.  GL, 73, Rich, K3VAT

Logged
W2WAW
Member

Posts: 12




Ignore
« Reply #18 on: June 06, 2012, 02:15:22 AM »

Hello, I am currently using the 4btv with 6 radials per band and I have no guy wires. I did use the thick wall pvc and traded the stock antenna clamps for stainless bolts so the antenna would fit inside the pipe. I covered the bottom section with a pvc fence post cover ( square 5x5) that I found at lowes, I did use the recommended rf choke at the base of the vertical along with a 5 ft metal fence pole driven in the ground and an 8ft ground rod to tie the radials to. It has a 3x5 nylon flag and the best part is neighbors have made compliments(snicker). It was a fun project. Good luck. 73 Mike w2waw
Logged
KC9RAK
Member

Posts: 22




Ignore
« Reply #19 on: November 21, 2012, 12:23:02 PM »

Wanted to give an update.  My 4BTV Flagpole is up and looks great!  I put down 45 radials ranging from 8 to 45 feet and did the midnight commando tuning routine.  Went with the DX Engineering Radial plate and Tilt Base.  Very difficult to tune without the tilt base with the weight of the PVC on there and all but pretty easy with the tilt base.  Disguised it all by getting a big flower pot from Lowes, painted it black, cut a hole in the bottom and slid it on upside down.  Have a great picture of it if I can figure out a way to post pictures here.

One problem... can't get 40M to tune.  Using a MFJ-259b and 6 feet of coax results in the SWR dip around 7.950  Have lengthened the 40M tube as far as possible.  Thoughts?

Thanks!!!

Dave 

Logged
W8JX
Member

Posts: 5588




Ignore
« Reply #20 on: November 21, 2012, 12:56:32 PM »


One problem... can't get 40M to tune.  Using a MFJ-259b and 6 feet of coax results in the SWR dip around 7.950  Have lengthened the 40M tube as far as possible.  Thoughts?


I would try more than a 6 foot stub to check it with. You might try temporarily adding a piece of wire with a clamp to top of it to lengthen it to see if it lowers resonance. It uses the total length to tune 40. Since you removed spider it reduced top loading. You should have used 6BTV maybe.
« Last Edit: November 21, 2012, 12:58:42 PM by W8JX » Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
WB0CJB
Member

Posts: 38




Ignore
« Reply #21 on: November 23, 2012, 01:17:17 PM »

I would recommend you stay with the 6BTV. However for 80 meters use the RM-80 mobile resonator.You can use a tuner to tune it on 80 anywhere in the band you want to go. I have the kilowatt resonator on mine and in a good 40+ MPH wind it sways quite a bit without guying it.So since I have the kilowatt resonator I have to guy mine.All fine and good until a neighbor mows your yard and winds up catching the guy with his riding mower (folded the antenna just below the 10M trap).But I have it repaired and the antenna was outstanding at field day with only 6 radials.

As far as tuning it the best way is to assemble the antenna by the dimensions in the instructions then borrow a MFJ-259B analyzer and tune the traps. It sounds like a lot of work but tuning the traps is the fastest way to tune the antenna. Adjusting the dimensions does not really help any at all.

The radial plate - there isn't any reason why you can't cover it with mulch. Just dope the bolts with anti-seize compound to help in taking it apart in the future if necessary. The radials can be 25 feet in length and  I run about 20 on my 6BTV.I have them tacked down with the sod or landscape staples you get at Lowe's or Home Depot.Once the grass grows over it you can run the mower over the area and not have to worry about snagging one or being able to see them.I use 14 gauge stranded insulated wire
for my radials.

I have seen a picture of someone who used a 4BTV and disguised it as a purple marlin birdhouse. All 3 antennas are excellent ones and I would not hesitate a split second to recommend any one of the 3 models. You might look through the past QST or CQ magazines as I remember seeing someone who lived in Florida in a mobile home park disguise his 6BTV as a flagpole. The pictures of it was quite impressive. Good luck and see you on the air. Feel free to contact me if you have any questions.

Paul WB0CJB
Logged
KC9RAK
Member

Posts: 22




Ignore
« Reply #22 on: November 23, 2012, 08:27:51 PM »

W8JX, I'll try a longer piece of coax to see if the readings change.  Couldn't do the 6BTV... HOA wouldn't agree with too much over 20 feet and we get very windy here so I'm not sure how the 6BTV would do disguised as a flagpole in the wind.

Paul, for reasons listed above, can't go with the 6BTV.  I did tune it exactly like you suggested.  Assembled it per specs, move all the traps down and got great tuning on 10, 15, and 20 meters.  Just can't get 40 to tune.  No capacitance hat being that it's a flagpole.  Will cover up the radial plate with mulch or perhaps some stone.  The flower pot only leaves one corner exposed and I have some landscape netting covering it for now.

Dave
Logged
WB0CJB
Member

Posts: 38




Ignore
« Reply #23 on: November 24, 2012, 07:13:03 AM »

Glad to hear you are well on your way. I do remember reading an article about the 40 M issue.The person that had the problem ended up adding a short coil at the base. Let me research that and I can send you the link or let you know what he did to get 40 to tune. I don't remember when I had a 4BTV if I had problems with 40 or not. Did you do the 10 turn RF choke coil in the coax like Hustler said? As I type this I'm not in the shack but if you will let me I will get back with you via email later today.I assume your email is in QRZ.com?

When I had my old 4BTV I had problems with SWR until I put the choke coil in as per Hustler's instructions. It (the SWR) dropped like a rock and I worked DX and statside like no tomorrow.
Logged
WX7G
Member

Posts: 5944




Ignore
« Reply #24 on: November 24, 2012, 07:50:45 AM »

To get 40 meters to tune you may have to adjust the top trap. I had to do this due to a good ground system. DX Engineering has directions.
Logged
KC9RAK
Member

Posts: 22




Ignore
« Reply #25 on: November 24, 2012, 11:07:24 AM »

Thanks, I'll have to go back and read but I thought the top trap on the 4BTV was the 20 meter trap.  Is there a way to adjust this 20 meter trap to get 20 meters in tune and also 40?

Dave
Logged
WB0CJB
Member

Posts: 38




Ignore
« Reply #26 on: November 24, 2012, 05:37:06 PM »

I found the article. If you Google K7CIE he has an article where he is installing a 6BTV but has issues with the 40 meter tuning. In his installation he had to put a 5 turn coil between the base tube and ground (he has a picture of it in the article). However, I never had any problem getting mine to work on 40. I did have to slide the top tube about 6 inches up to get it to fall into the 40 meter band.

Getting back to your antenna, yes the 20 meter trap does tune for 20 meters but it also can affect how 40 meters tunes. If your 20 meter trap is set and you are happy with your reading I wouldn't mess with it. I would think that if you slid the top section (the piece of pipe with the threaded stud) out maybe 6 inches then check the tuning on 40. If your 40 meter reading is better above 7.300 then the antenna is too short. If its better below 7.000 then its too long. But don't trim the aluminum tube (or any tube) whatsoever. There has to be a reason why your 40 meter SWR is finicky.

The difference between the two (4 versus 6BTV) is an additional tube and 30 meter trap for the 6BTV where the 4BTV has only the the capacitance hat. I can't see where the hat would make that much difference. All you are doing is removing the hat and omitting the tube and 30 meter trap. So what would happen if the top tube needed to be lengthened to the same physical dimension as the tube and 30 meter trap? The 30 meter trap is essentially invisible to a 40 meter signal. So whats left? A 24 inch tube plus the physical length of the 30 meter trap assembly. So if you tried a length of aluminum tube that is longer than you need then see what effect the tube has on the 40 meter SWR. I know DX Engineering has lengths of aluminum tubing as well as you could get the lower tube for the 4BTV. Attach it to the top of the 20 meter trap then see what the SWR is.

Let me know how it goes. I would love to see how your installation is. Its got me curious as heck!!! You can send me the pics to my email address on QRZ.com.

Paul WB0CJB

« Last Edit: November 24, 2012, 05:47:31 PM by WB0CJB » Logged
KC9RAK
Member

Posts: 22




Ignore
« Reply #27 on: November 24, 2012, 06:55:48 PM »

Thanks Paul!  I sent you an email with the picture...

Dave
KC9RAK
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!