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Reviews For: Diamond SG7900

Category: Antennas: VHF/UHF+ Omnidirectional: verticals, mobile, etc

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Review Summary For : Diamond SG7900
Reviews: 40MSRP: 119.99
2meter and 70cm mobile vertical
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
VE3PLO Rating: 2010-01-17
Save your money !!! Time Owned: 6 to 12 months.
Worked, when worked. After about 4 months of owning it, the antenna separated at the black coil. The solder went kaput, and the glue at the coil cracked and separated. Not something i expected from the most expensive DUAL band mobile vhf/uhf antenna out there. Save your money, buy a Diamond S285M or M285S--- something like that. It is just a whip, is tunable to 2m. Comes with a chart etc.. and the best part!!! i paid 30$ for it at the store.
M6KIM Rating: 2009-07-29
Very Good Indeed Time Owned: more than 12 months.
I've been using my SG7900 daily for over a year now. I'm confused by some reviewers comments because mine:

Has never failed or snapped over even at regular speeds of 70MPH+.

Nothing has broken.

There has been no water ingress.

It consistently gives good performance on both 70CM and 2M with low SWR and good penetration and range over various terrain.

It's the best VHF mobile antenna I have ever owned and i've had a few.
KJ4EOZ Rating: 2009-06-19
VERY HAPPY WITH IT !!! Time Owned: 6 to 12 months.
I have this Antenna on my wifes car its up very high in the air and It works great !! RX & TX I think this is the best antenna you can buy for 2 meters and 440 .
She runs it with a FT-7800R .
She has hit things with this antenna its a tank !
Maybe some of the guys on here are hitting things at 80mph . Or just have no luck with antennas . I have 6 Diamond antennas base and mobiles and all have been great !!
73s all / KJ4EOZ
K1SJC Rating: 2008-09-12
No thanks! Time Owned: more than 12 months.
When it works - it works great. BUT... This is my 3rd catastrophic failure in well under 4 years (the first failure was a physically broken lower load coil covered just before the warranty expired). That's not acceptable to me. Let's just say this expensive antenna has quite the appetite for replacement parts! The TCO adds up quickly.

Diamond got me for the burned out phase capacitor in my last review - and now, that one has burned up too. A call to RF Parts, asking what the deal is - and they indicate it can happen if water gets into it. This 60 inch antenna is mounted as low as it can go on the driver's front fender. I don't know how water is getting into it. They want $17.25 for another one (who knows what the shipping is), so I said "no thanks" I'm done with the SG7900A (probably Diamond, too). Warranty is 1 year on the whole antenna and 90 days on parts. Steer clear of this money pit!

Earlier 2-star review posted by K1SJC on 2007-03-08

I purchased this antenna thinking it would be ideal for use with my FT-100D. It works GREAT! SWR was 1.5:1. The gain specs are great, but with that, there are drawbacks. At 62 inches in length, it hits *everything*, the wind load at highway speeds makes it require a heavy duty mount (KC400 variety) - forget about mag mounts. There's no spring at the base, so the set screws tend to want to vibrate out - check them regularly or use nail polish to "seal" them in place.

Diamond replaced parts of this antenna under warranty for me. The antenna physically broke into two pieces at the plastic insulator where it wraps around the lower phase coil. Free replacement parts is good, but it was under warranty. After a total of a little over 2 years, the antenna somehow "burned up" the phase capacitor. I refuse to spend money on parts to repair it.

Diamond needs to either re-engineer this antenna or market it as an antenna for use on say, a mobile home - something that doesn't get used as a "daily driver". My opinion is that vibration is killing the antenna. I don't know what caused the blackened burn out on the phase capacitor - as my FT-100D does only 50 watts on 2M and 20 watts on 440.
VK4TZA Rating: 2008-08-30
Good for TX gain Time Owned: 6 to 12 months.
The SG7900 TX was very good TX. RX is comparable with the other units I have own. It’s not really all that robust, and I was concerned that the unit would fail in an off road situation (in my 4X4) . For this reason I was willing to sacrifice the TX gain and stick with more robust constructed Comet.
SV2BWM Rating: 2008-05-01
Drive slowly with that! Time Owned: 0 to 3 months.
It's a very good mobile antenna with SWR <1.5 and lot of dB's (VHF:5/UHF:7.6), but you must drive slowly and not in very windy roads! Even if you have a good magnet mount in the rooftop you could have the antenna ripped apart from the wind! Now, I have it installed in the back of my house's balcony and everything is OK...LOL
KG6JBL Rating: 2008-03-10
Gets out very well Time Owned: 6 to 12 months.
I use this with my D710 and used it with my D700. In Nevada I was hitting digipeaters at 200+ miles regularly. Construction is high quality and I haven't had any issues with bits dropping off or braking, but it is tall so I don't take it through drive-throughs on my F-250, I have once or twice and it didn't seem to come to any harm. If you find the screws coming loose then the proper products to use are red or blue Loctite, depending whether you don't or do intend every to be able to remove them again.
KF7FLY Rating: 2007-06-30
Poor mechanical construction Time Owned: more than 12 months.
Similar to my review of the SG7500.
The spring loaded break-over design will not stay up at highway speeds after a couple of months. These antennas looked promising, as they seem to function well. But the mechanical design is lacking. I also tried a SG7500. The same problem with the spring loaded break over happened to the SG7500. Also see my review on the K9000 motorized mount.

WD5M (previously KF7FLY)
KF6PYF Rating: 2007-01-28
Poor 2 meter performance Time Owned: more than 12 months.
I can't believe so many people have given this antenna such a high rating. Performance on 70cm is acceptable but its 2 meter performance is dismal.

Diamond rates their antennas in dbi not dbd. So to accurately compare this antenna to say Larson who conservatively rate their antennas in dbd you must subtract 2.15 db from the Diamond antennas. That puts the gain on 2 meters at slightly above unity gain at 2.8 dbd and 5.4 dbd on 440. Basically on 2 meters the Diamond is not much better then a $20. 1/4 wave whip.

Since the performance on 2 meters was so dismal I decided to replace the diamond with two dedicated Larson mono band antennas.
I used the NMO 440b on 70cm and the NMO 150b on 2 meters. While the gain figures on paper are only slightly better on 2 meters at 3 dbd vs 2.8 dbd and slightly worse on 70cm. The actual real world performance is substantial with the dedicated Larson antennas winning hands down.

Not only is the cost of two mono band Larson antennas including mounts cheaper then a single Diamond dual band antenna, they are much more durable. If you have the roof top real estate I strongly recommend using dedicated mono band antennas. If you can only mount a single antenna then I guess the diamond is acceptable. Considering that the diamond is only slightly above unity gain on 2 meters I think its a tad over priced.

The performance difference between the antennas could have a lot to do with Larson conservatively rating their antenna's (worse case scenario) in other words the minimum gain you should expect under the worst possible conditions vs Diamond's rating of (optimal) the best you could achieve under theoretically ideal conditions, we all know no mobile installation is optimal. Therefore rating a mobile antenna using theoretically ideal conditions is deceptive at best.

I am now using my diamond dual bander on my Camaro Z28. Unfortunately the t-tops reduce the roof top real estate so much that two antennas are not feasible.

Final thought.
You wold think that two mono band antennas would be more obtrusive then a single dual band antenna. Fortunately the opposite seems to be true, it's been my observation that the mono banders lacking the multiple large coils are far less visible. Another thing to consider is the Larson mono band antennas easily survive tree strikes and vibration that would absolutely destroy the Diamond.
KF5OK Rating: 2007-01-01
Great Performance, not Ruged Time Owned: 6 to 12 months.
Don't put this antenna on a ruff ridding vehicle or where it will continuously collide with obstacles. Mine failed after about 6mo.

My intallation was on a lifted jeep Wrangler. Rough, yes, I should have realized before i bought and the info was out there. the failure was at the plastic base with cracking and bad conntact to the metal base that attaches to the mount.

Now for the good. After replacing my NR770 I Was immediately rewarded with perceptible performance gains. On simplex i got a reliable 5-7 miles improvement to other mobiles. On repeaters my signal increased 1-2 S units over the 770. It was like having a 200w amp with receive benifits.

This antenna will be a must have list if i ever get a smooth riding sadan with a metal trunk.

Until then I think I will pick up an SG7500