I’ve been running a 80-10 off center fed dipole with the feed point at 45’ for a few years. I’ve been thinking of switching to a fan dipole. The ocfd is fine just wondering if a fan would be better. Any opinions on a difference between the two? Is one better than the other?
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Ofcd vs fan dipole. Opinions?
- Thread starter nfsus
- Start date
fan dipole installed correctly works pretty good.
solar cycle is running strong now so about anything that will lump a signal out will work.
With a fan you can tailor where the antenna is resonant at for what portion of the band you want to work.
OCF you sort of use what you have a touch up with tuner.
OCF is easier to build and install.
Fan is of course multiband direct fed no tuner required,,sort of.
PIA to tune.
transmits lobes same as a typical dipole if installed at least 1/2 wl agl.
Build one and have fun.
solar cycle is running strong now so about anything that will lump a signal out will work.
With a fan you can tailor where the antenna is resonant at for what portion of the band you want to work.
OCF you sort of use what you have a touch up with tuner.
OCF is easier to build and install.
Fan is of course multiband direct fed no tuner required,,sort of.
PIA to tune.
transmits lobes same as a typical dipole if installed at least 1/2 wl agl.
Build one and have fun.
I realize this is an older thread, but ...
I've used both, and my current HF multiband antenna is an OCF dipole, while the very first HF antenna I made and put up after I got my ticket was a fan dipole. The fan dipole seemed to work fine, but it was cumbersome to pull up and down to tune, and very ugly spreading it's 5 dipoles in our total backyard sky. I didn't run it long. I took it down in favor of a skywire loop I ran on 80 - 10. I've tried several different multiband antennas. I have settled on the OCF.
The OCF is vsually tame. Easy to get right, and both my manual and auto tuner sit unused on the shelf as the internal tuner in my IC746 had only to tune each band (which it did with ease) only once and never forgot. I cut it for the lowest band, 80m, and the tuner isn't needed there.
Yes, I'll probably tinker with other antenna types for fun at times, but I will use this one as long as it serves me as well as it has.
"CQ, CQ 20, Kilo 5 Hotel Bravo Bravo calling CQ 20 meters..."
I hope to meet you on the air somewhere between 1 watt and 100.
I've used both, and my current HF multiband antenna is an OCF dipole, while the very first HF antenna I made and put up after I got my ticket was a fan dipole. The fan dipole seemed to work fine, but it was cumbersome to pull up and down to tune, and very ugly spreading it's 5 dipoles in our total backyard sky. I didn't run it long. I took it down in favor of a skywire loop I ran on 80 - 10. I've tried several different multiband antennas. I have settled on the OCF.
The OCF is vsually tame. Easy to get right, and both my manual and auto tuner sit unused on the shelf as the internal tuner in my IC746 had only to tune each band (which it did with ease) only once and never forgot. I cut it for the lowest band, 80m, and the tuner isn't needed there.
Yes, I'll probably tinker with other antenna types for fun at times, but I will use this one as long as it serves me as well as it has.
"CQ, CQ 20, Kilo 5 Hotel Bravo Bravo calling CQ 20 meters..."
I hope to meet you on the air somewhere between 1 watt and 100.
The ocf and fan dipoles are really two different antennas, and there really isn't much that is directly comparable.
A few things I noticed while modeling these antennas.
1) With the fan dipole, it is easier to predict the radiation pattern. On some frequencies, the pattern of the ocf is almost random in comparison. Add to the fact that in a real world setup, you are likely using two trees that you can't move to aim the radiation pattern in a beneficial direction (or directions). So for this it is hit and miss.
2) The fan dipole is consistently more efficient. Its a very small difference, but there is a difference.
3) The ocf dipole has more directivity, and sometimes quite a bit more, comparitively speaking.
4) As you go higher in frequency from the lowest frequency, these antennas have peak gains in completely different directions from each other. Also, the ocf dipole tends to have higher peak gains (and actually lower angles of about 10 degrees on the 20m and 40m bands, yea this one surprised me) overall...
Anyway, some comparison models, starting with 80 meters.
Its not shown here, but peak gain for both is straight up... At this frequency, very comparable results.
40m
Here we see a pattern form. The antenns are along the x axis, and the ocf feedpoint in to the left of the 0 point of said axis. The fan dipole's gain tends to be broadside of the antenna while the ocf dipole's peak gains are about 45 degrees out from the broadside pattern, with a deep null not quite broadside of said antenna.
20m
Essentially, more of the same. The fan dipole is still has the predictable broadside pattern while the ocf peak gains are between 55 and 60 degrees off broadside.
And finally 10m
The predictable fan dipole is more of the same, but the ocf is a real mess. Peak gain for the ocf is between 65 and 70 degrees off of broadside.
You could literally have these two antennas up side by side and have contacts on either that the other will have trouble pulling in. In some cases, one will get you more contacts, and in others the other one will, it simply depends on the antenna layout, and the direction said contacts are at.
In real world installs where I am limited by a few trees, I'de go with the ocf dipole. If I am using frequencies that are high enough that I can mount the antenna on a rotor, I would go with the fan dipole for the predictibility.
You can factor trap dipoles into this as well. They will be very close to the fan dipole, but as you go down in frequency, there will be a hit to effeciency because of the traps, so the more bands it can hande, the less effecient the lower bands will be... It would also be smaller in length than either of these antennas, so for some people may be their only option to fit something like an 80 meter multi-band antenna in their yard...
The DB
A few things I noticed while modeling these antennas.
1) With the fan dipole, it is easier to predict the radiation pattern. On some frequencies, the pattern of the ocf is almost random in comparison. Add to the fact that in a real world setup, you are likely using two trees that you can't move to aim the radiation pattern in a beneficial direction (or directions). So for this it is hit and miss.
2) The fan dipole is consistently more efficient. Its a very small difference, but there is a difference.
3) The ocf dipole has more directivity, and sometimes quite a bit more, comparitively speaking.
4) As you go higher in frequency from the lowest frequency, these antennas have peak gains in completely different directions from each other. Also, the ocf dipole tends to have higher peak gains (and actually lower angles of about 10 degrees on the 20m and 40m bands, yea this one surprised me) overall...
Anyway, some comparison models, starting with 80 meters.
Its not shown here, but peak gain for both is straight up... At this frequency, very comparable results.
40m
Here we see a pattern form. The antenns are along the x axis, and the ocf feedpoint in to the left of the 0 point of said axis. The fan dipole's gain tends to be broadside of the antenna while the ocf dipole's peak gains are about 45 degrees out from the broadside pattern, with a deep null not quite broadside of said antenna.
20m
Essentially, more of the same. The fan dipole is still has the predictable broadside pattern while the ocf peak gains are between 55 and 60 degrees off broadside.
And finally 10m
The predictable fan dipole is more of the same, but the ocf is a real mess. Peak gain for the ocf is between 65 and 70 degrees off of broadside.
You could literally have these two antennas up side by side and have contacts on either that the other will have trouble pulling in. In some cases, one will get you more contacts, and in others the other one will, it simply depends on the antenna layout, and the direction said contacts are at.
In real world installs where I am limited by a few trees, I'de go with the ocf dipole. If I am using frequencies that are high enough that I can mount the antenna on a rotor, I would go with the fan dipole for the predictibility.
You can factor trap dipoles into this as well. They will be very close to the fan dipole, but as you go down in frequency, there will be a hit to effeciency because of the traps, so the more bands it can hande, the less effecient the lower bands will be... It would also be smaller in length than either of these antennas, so for some people may be their only option to fit something like an 80 meter multi-band antenna in their yard...
The DB
My OCF feedpoint is 2' above my roof, 18' above the ground. The longer leg rises 4' at 25' from the feedpoint, then bends 80° rising to 30' above ground at ~32' out then dips to about 12' above the ground. The short leg runs opposite direction from the longer from the feedpoint rising 4' at 15' from the feed point also making an 80° turn the same direction as the long leg rising 25'.
Essentially a U shape with 49' between the bends due to my yard shape. I realize that affects the radiation pattern, but what's a city lot dweller to do?
Video starts at the dipped down end of the long leg. Feedpoint is on the chimney box.
Tornadoes came through here Memorial Day 2024 weekend and destroyed my better poles and tree tie-offs.
Essentially a U shape with 49' between the bends due to my yard shape. I realize that affects the radiation pattern, but what's a city lot dweller to do?
Video starts at the dipped down end of the long leg. Feedpoint is on the chimney box.
Tornadoes came through here Memorial Day 2024 weekend and destroyed my better poles and tree tie-offs.
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Sounds pretty complicated, if I get some more time this week I might try and get it into the modeling software... No guarantees though, I can't say translating that into a model will be easy...
The DB
Having built and used both antennas.
Both have pros n cons.
OCF
easy to get working effectively.
lightweight,( yes us old farts pay attention to weight )
Cons
Skewed pattern on upper bands.
fan.
effecient balanced antenna
radiation pattern and more important the NULLS can be predicted and antenna installed accordingly.
Cons,
,heavy,,ugly,,pain in ass to tune ( reminds me of me)
Both have pros n cons.
OCF
easy to get working effectively.
lightweight,( yes us old farts pay attention to weight )
Cons
Skewed pattern on upper bands.
fan.
effecient balanced antenna
radiation pattern and more important the NULLS can be predicted and antenna installed accordingly.
Cons,
,heavy,,ugly,,pain in ass to tune ( reminds me of me)