Problem with a diamond antenna x510hdm x510 x510n vhf uhf


My diamond antenna x510 hdm (x510hdm), that was selected to handle my 160 watts amplifier, stopped working last week-end.

I suspected that a capacitor blew since it happened while I was transmitting. I ordered the “high power” diamond antenna so this wouldn’t happen. It happened. The swr where it happen would read at 1.3 1.4 swr normally. The antenna is rated to 330 watts and it’s probably PEP with 1.1 swr. If the swr raise the capacitors inside doesn’t handle enough voltages to get close to the 330 watts rated.

I contacted (call, message, call, message, email, call, message …) radioworld, where I got the antenna not long ago, and they couldn’t help me and asked that I deal with the diamond antenna north america distributor. After many calls and couple email I gave up on trying to get any return from them in a reasonable time. Diamond antenna america is a division of rf parts company and I’ve had a very bad experience dealing with them in the past (support to Canadian market).

I took my chance with diamond antenna Japan and got quick reply to my emails (couple hours delay) and they gave me confirmation of the value used in the x510hdm since it’s different than a x510n or x510.

They also told me some antenna would come with 1000v caps and others with 500v caps. I’m not sure which one I have but my “not exploded” capacitors where 3pf and 11pf. The missing value was in serie with the 11pf and they confirmed me it was a 12pf 1000v that should go there. I got the confirmation from them edited on a picture. I’m adding the picture directly here if can be of future help for someone else.

I will try to source the part locally and replace it, if I don’t post any follow up it’s because everything went well.

BTW did you know a X510 antenna is resonant in the 220mhz band ? I’m using mine as a triband antenna to reach 220 mhz repeater up to 30-50 miles without any problems.


73, VA2SM

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12 Responses to Problem with a diamond antenna x510hdm x510 x510n vhf uhf

  1. Albert says:

    Greetings, I have the same antenna (x510hdm) with the same capacitors at the bottom that needs to be replaced but I cannot find the values for each one. If you can please help me decipher the values for each ones and their replacements (3c, 12 J KCK and 11 J KCK), thank you.

  2. Louis Gagnon says:

    Bonjour Sylvain , ce serait tres agréable si tu avais un blog en Français. Je comprend un peu l’anglais mais il me manque souvent des ti bouts…..bonne journée Louis ve2 hwd

  3. David Martin says:

    Were can I get capacitors that will allow me to operate ie 160watts.I was using 40w and they gave up. I ve asked around here no one seems to know or care all they say is the values are rare and hard to locate.

    • Sylvain says:

      Hi David,

      The wattage is not the only variable that limit the operation on this antenna. If you have a swr of 1:1 of close to a perfect 50 ohms load you could put probably 200-300 watts and the capacitors wouldn’t see enough voltage to blow up. With a higher swr like 2:1 or a 100 ohms load that same 200 watts would get the voltages at the capacitors in the thousands of volts. So what you need is to replace the capacitors with either the original 500 volts ceramic version or like I did, get 1000v ceramic 12pf capacitors. They are larger so it can be a tighter fit. Now that I know that the max power the antenna can take is dependant of the swr, I try to limit to 100 watts when I’m over 1.5:1 swr but when I’m under that swr I use close to 200watts without any problems.

      Those capacitor have an effect on the tuning of the antenna so if you get some, purchase more and try to measure them to get the most accurate one possible. I didn’t and ended up pushing the middle of the vhf bell curve at 146.400 instead of 146.000 like before I changed the capacitor. Next time I remove the antenna for inspection I will change them for more accurate capacitors that I’ve selected.

      Good luck with your repair, let me know if you need more informations. VA2SM

    • Owen Baldwin says:

      Hi David, you may already have you’re replies, but you can double the capacitance original value and put 2 in series, which will give you the original value, but double the voltage tolerance ie 5pF @ 500 working volts x 2 in series will give you half= 2.5 pF which is the original specified value in this one example. But, will handle double the voltage to 1000 working volts, allowing more power.
      Hope this helps.

  4. Johnboy says:

    I own this antenna and the bottom line is it’s a piece of shit!

  5. Brian Robinson G4ZEK says:

    I wonder if these mods will work on the Diamond X7000 2M/70Cms / 23cms Ant .

  6. Dylan says:

    i have mine too, and it’s working better with my matching ICOM 2200 or YEASU mobile base., it’s perfect..

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