I have been looking for a suitable 2/70 antenna, saw this J pole, unfortunately, this one comes in at around £23.00, but with shipping from the States over double the price! I will see if there are any 3D plans for it!
Make it yourself, you are a radio amateur!
And… make a Flowerpot instead. My 2m Flowerpot took 45mins to make and is much more tolerant of nearby stuff than my J-pole and works exceptionally well on 70cm. A bit of wire, a bit of scrap RG-174, a PVC overlow pipe cutoff and a plug. Simples!
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There is a reason I want a roll up antenna
Buy a few meters of 300-ohm or 450-ohm ladder line; you can find many online calculators for the lengths of the sections. I recommend the Slim Jim instead of the J-pole. As soon as I have time, I’ll send you the measurements of mine for 2 meters.
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You’re absolutely correct. Flowerpots are an absolutely nightmare to roll up 
2m Flowerpot with 5m feeder, rolled up with USB memory stick for scale.
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This
Easy to build and roll up. Part cost of 12 Euros or so.
I use Rg-316 coax and an SMA connector for my handheld. Trusty companion since many years of activating.
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Spectrum Communications if you want to buy one. He has an ebay store.
My one has been abused for years and still works well.
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Don’t forget that the US allocation on 2 metres isn’t quite the same as ours, so a US-made antenna might not be that great here…
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I already have one; the signals it receives are ok, but I have had lousy signal reports. I think last time I used it, I swapped back to the high-gain whip on the HT
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They say it’s for 144 to 146, but I’m not looking to buy because of postage. I’m interested in making one, but obviously getting the required bits 3D printed
Have you considered why this may be? It may not have been the antenna.
Measure of my slim Jim:
The stub abt 45 cm, feedback point at 8.5 cm. Radiator abt 108 cm and 2 cm of gap. Coax rg174.
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Tried it with different HTs, different connectors, and the same cable, and got the same result. I need to get it on the NanoVNA-H4 and see if that tells me anything.
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Is yours the 2m monoband version, or the 2/70 dual bander? I’ve got the 2m monoband and it’s been almost certainly the best £23 I’ve spent on radio gear!
(Now there’s a question: 100% of a slim G vs about 50% of an FT-270 for the best £23 spent award…)
If a J-pole or a Slim Jim resonates at 144 MHz, then it also resonates on the third harmonic at 433 MHz.
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But a large portion of the radiated power does not reach the receiving station; instead, it travels along the wire and is therefore lost.
Any antenna manual will tell you how the radiation pattern deteriorates as soon as a wire is longer than 5/8 of a wavelength. It’s easy to test in practice: the rubber antenna on a handheld radio will then have a stronger signal.
73, Peter - HB9PJT
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I didn’t know this detail. I only knew that at 5/8 wavelength the lobes are flatter and better suited for DX; this applies to vertical antennas. I believe it’s the same for J-pole and Slim Jim antennas as well.
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Same. Ordered direct from Spectrum and shipped to EI so I paid a little more in postage and tax/duty but well worth it.
Used it squillions of times and it has paid for itself several times over. Love it.
I should look in to a 70cm one but the RH770 does a good enough job for now.
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A standard 2m J-pole (the Slim-JIM is just a variant with no significant difference in performance) is a half wave radiator - basically a dipole. On 70cm it is a 3/2 wave radiator. The radiation patterns look like this: 2m is blue, 70cm is red.
When the antenna is perfectly vertical, the signal on 70cm is less than 2 dB down from a dipole. But if the antenna blows in the wind, or the pole leans, so it is 15 to 20 degrees off vertical, then the signal can drop significantly in some directions due to the nulls in the vertical pattern.
There are several ways to improve the pattern on 70cm, and several attempts to do so that don’t actually work very well.
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