I am looking to replace my DB224 antenna as I’m pretty sure it has water in the phasing harness. Suddenly after a rain the repeater is going to low power mode when transmitting. Hooked my watt meter up and a 50 watt mobile to the coax and was getting around 35 watts reflected all of suddenly after this rain we had, used to be around 1 to 2 watts reflected. Really sucks since the antenna has only been up at 300ft on a tower a couple months now. Looking at possibly going with the Sinclair SD224 for an Omni-directional VHF antenna. Anyone on here have any experience with the SD224?
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Sinclair SD224
- Thread starter TrevorMollenbeck
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kayn1n32008
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I'd pass on an SD224. My choice would be a SRL210C4 1/2 wave spaced. It's an internal harness and is well protected from the elements.
dapaq2
Member
But does Sinclair still make and offer the SRL 210 C4 ??? The model you suggested appears to be a discontinued EOL model, not finding any "SRL" models of any variation listed in the Sinclair catalog. And doing an internet search on that model the results seem to indicate that it has been discontinued for many years, a few websites are indicating it is 'obsolete' and no longer provide images or product literature. If it has been discontinued, and several years ago, it will most likely be a challenge for him to find an SRL 210 C4, especially a brand new one.
Sinclair recently realigned their model matrix to align with their other products. the SD214 is the internal harness 1/2 wave.
Excellent performing and broadband antenna. We use them on all of our VHF sites here.
Excellent performing and broadband antenna. We use them on all of our VHF sites here.
Ubbe
Member
I haven't looked close enough at the DB224 but it seems to be less likely to be a water intrusion in the antenna but more of the coax.
At my work we always use Aerial Oy stacked dipoles that are welded aluminum and I haven't seen any of those antennas fail, even one that where thrown down from a water tower and had a bent dipole could still be used. But I have several cases where there have been water in the feeder coax due to connector installation issues and of course glassfiber antennas get old and brittle and can get cracks that sucks in water.
/Ubbe
At my work we always use Aerial Oy stacked dipoles that are welded aluminum and I haven't seen any of those antennas fail, even one that where thrown down from a water tower and had a bent dipole could still be used. But I have several cases where there have been water in the feeder coax due to connector installation issues and of course glassfiber antennas get old and brittle and can get cracks that sucks in water.
/Ubbe
I was looking at this antenna also, do the 4 elements need to be arranged so one element is on each side to make it Omni-directional? I seen it said it is a bi-directional antenna and am curious if arranging the elements like the DB224 would make it an Omni or not?Sinclair recently realigned their model matrix to align with their other products. the SD214 is the internal harness 1/2 wave.
Excellent performing and broadband antenna. We use them on all of our VHF sites here.
kayn1n32008
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The elements on a SD214 are fixed and not adjustable, while it is technically an 'offset' pattern, in reality, you won't notice it.
kayn1n32008
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See the reply addressing this. My apologies, we still call them 210-C4's where I live. But yes, they still make them. Search SD214
Ok, I wasn’t sure if that would make a noticeable 8 pattern around the tower or not. From what I read in previous threads that looks like the antenna everyone seems to like. I just was sure about it at first since it was listed as bi-directional but if it works just as good an Omni I’d definitely give it a try! It does look like a really good antenna.
kayn1n32008
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Keep in mind, any antenna side mounted to a tower, is going to have some degree of directionality to it caused by tower shielding.
Ubbe
Member
In many cases you are not using a tower in the middle of the coverage area. There might also be terrain issues that needs a higher level of RF coverage in a certain direction or the towers location needs the antenna to have more coverage in a specific direction and having all stacked dipoles pointing in the same direction and being installed at one side of a tower could help to adjust for the best coverage. The distance between dipoles and the tower will also have an impact.
/Ubbe
freddaniel
Member
Before spending a lot of money on a new antenna, consider the possibility of bad Heliax cable. The ONLY WAY to know, is to climb the tower, disconnect the antenna and insert a thru-line wattmeter.
Or if you have an Anritsu S331 antenna analyzer, you can disconnect the antenna, short the feedline and sweep it with the TDR function to see any faults and where they are located. Sometimes when a crew works on a tower, a feedline may get punctured, bent, kinked or crushed along the way. Also, consider water in the top connector. Tape is not enough.
Take it from someone who owned and maintained 35 tower sites.
Also, the Sinclair SD214 is a wonderful antenna.
Or if you have an Anritsu S331 antenna analyzer, you can disconnect the antenna, short the feedline and sweep it with the TDR function to see any faults and where they are located. Sometimes when a crew works on a tower, a feedline may get punctured, bent, kinked or crushed along the way. Also, consider water in the top connector. Tape is not enough.
Take it from someone who owned and maintained 35 tower sites.
Also, the Sinclair SD214 is a wonderful antenna.
That’s what I figure too, might as well have it all checked out before ordering anything. I have a tower crew coming the end of this week to check everything out and see it actually is the antenna or if it is instead the coax. I definitely don’t want to drop thousands of dollars on something that isn’t even the problem!
I'd definately be sweeping the antenna as well as the line. There are alot of DB224's out there and if this was an issue more folks would have issues. I'd definatly check weatherporoofing and stuff for water. From the picture I only see electrical tape over the connection ?
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Several years ago, when I would do antenna work I was given a new harness, and I would replace the harness that was back in the days when the DB224 and DB420 were in the $1000 range.
There are still DB224's and DB420's that I put up over 30 years ago still up and working. I hated having to replace one of my antennas after a lightning strike due to how well I waterproofed the connection.
There are still DB224's and DB420's that I put up over 30 years ago still up and working. I hated having to replace one of my antennas after a lightning strike due to how well I waterproofed the connection.
prcguy
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The Heliax on this antenna should have been secured to the mast as it probably flops around in the wind. That will put a strain on the connectors. The last DB244 we replaced for the USCG was on a similar tower mount and a new tower leg mount was made that held the antenna out about 6ft from the tower. The new mount has a third member made of fiberglass U channel that attached to another tower leg and eliminated the chance of the mount rotating on the tower leg. Placing the antenna 6ft out from the tower improved omni coverage as it’s about 1 wavelength out compared to the stock mount at about 1/2 wavelength out.
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prcguy
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Edit, wrong info.
freddaniel
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Another possibility is the center pin of the antenna male N-type connector retracting or pulling out of the female on the Heliax, due to banging on the antenna mount, in the wind. As prcguy suggests, the Heliax needs to be secured near the connector to avoid tension on the antenna cable at the connector. View photos above. I have seen many N-type males with cables pulled back enough to make unreliable connections at the pins. In particular, types that use compression to secure the shield. That is why I only use crimp connectors, but many manufacturers still use compression connectors.
An update as to what was discovered when my tower crew came and checked everything out… They found a connection that was loose and not sealed good enough right where the coax connects to the polyphaser. They took the connector off and water dropped out of it. So they dried and cleaned the connector and got it tightened to the recommended torque spec. Then they properly weather sealed the connector. Repeater is working flawlessly again and I’m very glad I didn’t purchase a new antenna before they checked out the connectors, didn’t cost me anything for parts or labor this way so I’m going to consider that a win.
