5/8wave workman swr issues? Balun? Unun?

[BOOTY MONSTER]

IIRC , the workman/maco 58 is specked at 240 inches tall . i've wondered if adding another 2 1/2 or 3 ft to their length (making the vertical 22 1/2 to 23 ft tall) would help them perform better . anyone ever tried it ?

 

[The DB]

IIRC , the workman/maco 58 is specked at 240 inches tall . i've wondered if adding another 2 1/2 or 3 ft to their length (making the vertical 22 1/2 to 23 ft tall) would help them perform better . anyone ever tried it ?

Yea they did make it a bit short didn't they. In theory impedance should match assuming you are not right near an edge of the tuning ring to begin with on your current setup. At worse you would need to increase the size of the ring a bit and perhaps the length of the radials an inch or two.

Mind you as I said I haven't done this myself it is all speculation. I could see me playing with one but if it takes more then adjusting the tap for tuning then I doubt the gains would be worth the effort.

You would also have to separately purchase the longer aluminum, which is not very cheap. Would likely cost near as much if not more than the antenna to begin with...


The DB

 

[BOOTY MONSTER]

the vertical top piece (T01) is 1/2 inch tubing so 3/8 will fit in it .

http://www.macoantennas.net/files/MACO_V58.pdf

lowes has a 3 ft length for $5.20

Shop Steelworks Aluminum Round 3/8x3 FT at Lowes.com

leave 4-6 inches in the T01 1/2 inch piece .

I had to shorten the radiator 2.5 feet. .? much shorter than the listed 27mhz length in the instruction packet? Any ideas?? Help?

so if he's about 17 1/2 ft now he's closer to a half wave ....... but it should tune .....

 

[W5LZ]

Wanna make the thing 2 feet longer? Easy, just decrease the amount of inductance in the 'coil' by an appropriate amount (not feet/inches, but inductance). Resonance stays the same just length is changed. Any appreciable difference in radiation? Probably not, but I have no sure idea.
The difference in 'size' of the loading coil makes up for the lack of length, and visa-versa.
- 'Doc

 

[ghutch]

Ok....worked on this antenna without any real progress still swr at 1.5-7 on 1 and1.7-8 on 40
Tap is at the back...180 degrees from the coax connection, next to the bolted point where the two halves bolt up. Moved it towards the coax connector swr go up. Swr are very close channel 1 and 40 with the tap where it is.
Radiator from tip to bottom of base is 232 inches ...end to end measurement
coax coil added ...5turns on 4.5 inch PVC form..form was removed ,coils taped together an attached 3 inches from the coax connection made no change.
Radials are 108 inches long?? Shorten these??
Mast is inserted 6 inches bolt they hole...the mast is not inserted fully.
Coax is 53 ft 3 inches connector to coil...3 inch pigtail to connector
Read every post several times..maco manual,workmn manual, marconis manual,
Don't know where to go now

 

[BOOTY MONSTER]

when i made my home-made maco type 5/8 it tuned at about 9 o'clock to 9:30ish if you think of the arms for the ring as being at 6 o'clock . i didn't fine tune it though , i hit 1.3 and was happy enough .

 

[ghutch]

Make sure I understand this antenna design.???
The coil tube and tap match system match to the radiator and make this antenna electrically longer. This is to lower the ohms at the feed point? 50 ohms to match the feed line coax? Is this right?
The radials also play a part to lower the feed point ohms as well?? As well as angles on 1/4 wave verticals
Looking at a zero five 5/8 wave...they seem to have a similar matching system, just bent in a u shape on one side? They also have another tube or coil attached ? Is it the match or the bent tube coil with the tap?
With The ideal pattern of radiation a 5/8 wave gets it gain from the lower angles in the radiation pattern?? Thus a small gain over 1/2 wave antenna
Verticals at low heights have a lower radiation angle than most antennas over good ground? Under 1 wavelength high.

 

[The DB]

Make sure I understand this antenna design.???
The coil tube and tap match system match to the radiator and make this antenna electrically longer.

So far so good.

This is to lower the ohms at the feed point? 50 ohms to match the feed line coax? Is this right?

Not exactly. While this effect happens, what is actually happening is they are making the antenna electrically a 3/4 wave antenna. 3/4 wavelength is resonant. The resonant point of an antenna is also the low impedance point of that antenna, so in a round about way the effect you see happening is the same. However, very rarely is the best point to tune these, or any antenna for that matter, at 50 ohms of impedance.

The radials also play a part to lower the feed point ohms as well?? As well as angles on 1/4 wave verticals

The radials are a radiating part of the antenna. They are the other half of the antenna. Each half of the antenna does affect each other so yes, they will affect the feed point impedance. They also affect the radiation pattern of the vertical radiator. There is far more going on with them than simply to help with tuning.

Looking at a zero five 5/8 wave...they seem to have a similar matching system, just bent in a u shape on one side? They also have another tube or coil attached ? Is it the match or the bent tube coil with the tap?

Not being directly familiar with them I took a look. The piece you are referring to has the same effect as the ring in your Workman, however, they have something else attached to both the radiator and the ground plane portion of their antennas. As I am not sure what this does I don't know what affect it will have on their tuning.

With The ideal pattern of radiation a 5/8 wave gets it gain from the lower angles in the radiation pattern?? Thus a small gain over 1/2 wave antenna

Up to a point (just past the 5/8 wavelength point) as you lengthen an antenna it radiates less and less RF energy up, redirecting that energy out. This can lower the radiation angle, but it is also putting more RF energy into that lower lobe. That lobe will also be more sensitive on reception as well so it will affect your receive the same as it does your transmit.

Verticals at low heights have a lower radiation angle than most antennas over good ground? Under 1 wavelength high.

And yet they perform better higher up, at least locally. If DX is your goal a number of other factors come into play.


The DB

 

[BOOTY MONSTER]

http://www.worldwidedx.com/cb-antennas/100406-ought-worth-discussion.html

 

[HomerBB]

Their antenna matching network appears to have an inductor in the form of the ring, and a capacitor in the form of a sliding tube. It is similar to the matching network I have used for my EFHW antennas.

 

[The DB]

http://www.worldwidedx.com/cb-antennas/100406-ought-worth-discussion.html

I so wanted to like this post, if only it wasn't for all the pages of arguing in the linked thread... There was some good info about the antenna in question in there, thanks for the link.


The DB

 

[ghutch]

Guys don't leave in this antenna nightmare! The more I read the dumber I get??
This antenna theory is hard on my brain Dx. Is the main purpose for all this head scratching .... This antenna will be mounted at the water (saltwater)line during use at 10-20 feet....looking to get a lower radiation pattern to work Dx from the beach.
Making the antenna electrically a 3/4 wave for resonance and 5/8 wave for the radiation pattern? Is think ? Is this what is being attempted? I understand past .64 wave antenna pattern break up into many lobes and nulls....I want as low a radiation take off angle with the majority of the radiation in that low angle Lobe? Correct?
Radials....mine measure 102 inches. Would a be better to add another radial ring below the ones currently on the antenna...I have the parts and tubing.(ended up with 2 of these antennas?). Would this be the same as folks adding 120 wire radials to some verticals? I thought the mast would be the other half such as a dipole. Some models I have. Found on the web show the mast and feedline radiating? I have thought about adding wire radials around the mast laying on the ground but reading these must be a certain wavelength and would not be worth all the tuning....I can't get a simple antenna to tune so adding issues is the wrong way to go.

 

[HomerBB]

ghutch, did you read the instruction DB linked to for you?

If not, here it is again:


I have never failed to get a Maco to 1:1. Maco has never failed to have the wrong
dimensions in their instruction sheet. Sure, you will get ciose, but usually the published lengths are too long and Maco says, ""..however, the chart length is not sacred and may be changed...", so they give themselves an out.
Not knowing what your set up is, i suggest the following:
I set every element for 6" of overlap and adjust the TOP section for resonance (groundplane elements are 4" per instructions). Maco suggests adjusting "T43P" (second section).
I'd much rather have a solid 6" of overlap here. You will find that the top section will have close to 12" overlap. Since they use the weaker .047 material, this overlap will actually strengthen the top of the antenna.
Take your antenna down and double check all measurments. Especially check the location of the wire tap. It's VERY easy to have the tap on the wrong side of the loop! The wire should tap closer to bottom bracket (P08P).
Set the antenna up on a 10' mast in your yard. Have a friend hold it. Check for frequency with lowest SWR." If your radio goes out of band, keep checking until you find the frequency with the lowest SWR. If it below channel 1, then your antenna is too long. Tip the antenna over and adjust the TOP section in 4". Yes,4"!! Check SWR again and see if the frequency is now closer to where you want it to be. Keep adjusting the TOP section of the antenna until your lowest SWR is on the frequency you want (for me, it's ALWAYS channel 20).
Then, using a 6' ladder, move the tap in one direction and then the next until you get a dip in the SWR. It may read as low as 1.5:1 now.
Here is the important step that 99% of the people out there mess up on (except for
English Bob; he gets it). Check the FREQUENCY for lowest SWR again. It may be above or below your desired frequency. Adjust the top section in or out to bring the SWR down even further on your desired frequency, then re-adjust the tap on the loop! You will see your SWR drop even morel it should only take a couple of adjustments to get a PERFECT 1:1" SWR on your Maco.
What we have done here is adjust your main antenna element for resonance on your
desired frequency, and adjusled your feedpoint matching network to allow your 50-ohm cable to feed a 5/8 wave antenna. Don't be surprised if you can hear better and talk farther. 2:1 SWR may work, but it is far from efficient.
Once you're done adjusting ycur antenna, then re-install it on your tower. The SWR may change a bit when ycu put it up in the air, but it uvill only be siight. Adjusiing an antenna 10' off the ground has worked for 30+ years and is much easier than trying to so it on top of a tower Good luck!

 

[ghutch]

Yes....went thru it step by step...1.5.! Is the best I can get. Plan to xcomplete take it apart and start completely over.....coax checked out ok

 

[HomerBB]

You can operate at 1.5 with no problems. It may be that as was hinted at before the type of ground and your relative closeness to it might be a part of what you are experiencing. Personally, I'd run with it and then take a look at it when I got it back to where I was going to permanently install it.