Tuesday, September 4, 2012

Modifications to the Diamond V2000 and similar antennas

This kind of antenna has grown in popularity over the last years because it gives you a decent performance and triband capabilities. But its 50 MHz design is far from optimal. Here you can learn how to improve its 50 MHz performance in a very easy way.

The physics behind the V2000 is very simple. A 5/8 antenna on 144 MHz is almost a slightly loaded quarter wave on 50 MHz. So it is not very difficult to modify the matching network to use the lower 5/8 144 MHz element as a 1/4 wave element for 50 MHz. It's very easy to do. But a quarter wave vertical antenna antenna needs an earth plane to work properly. The V2000 antenna uses a quarter wave radial as a counterpoise for 50 MHz. This is the way its uses to get it working at the three band simultaneously.

There are many antennas working with this principle on the market. Some of them are: Moonraker SQBM-1000, Watson W2000, Comet CX-725 or GP-15 (a good article from K1LH about a similar mod for the GP-15 is here) and of course, the Diamond V2000. This modification have been performed on a generic V2000, but surely it can be done on all the others as well.

 The V2000 and similar antennas have a tuned radial for 50 MHz. Because only the first 144MHz 5/8 element works at 50 MHz, the antenna is not more than a rotated V dipole in this band, a rotated dipole in a way one of its arms is vertical.

The antenna was mounted about five years ago, and it has work always nicely on 2m and 70cm. On 6m I had TV (yes, I still have TV in VHF channel 2 here) noise, sometimes as high as 9+. But it has not been a problem to hear nice signals on the band, of course Es, and some nice TEP and F2. The antenna worked nicely... except if you test it with an antenna analyzer. The antenna had a very erratic SWR curve at 50 MHz, with many nulls between 48 and 56 MHz. The rig's SWR meter shown the same erratic curve. There was no dude the antenna had a problem.

My first try was to adjust the radial length, but the radial was fixed, no tuning possible at all. I tried to tune the antenna cutting physically the radial, but nothing except another erratic SWR curve was obtained. I restored the radial. Here I can't transmit on 50 MHz, so SWR was not a problem at all.

Some time later, playing with MMANA software, I modeled the antenna and I realized what was happening at the antenna. A quarter wave antenna really NEEDS a ground plane to work. Manufacturer do not provided a ground/earth plane for the antenna, only a tuned radial, or counterpoise as it is called some times. The problem is that a vertical quarter wave antenna with only a radial/counterpoise, isn't a vertical antenna. It's a DIPOLE. But it is a problematic dipole:

The dipole does not have balun, so the coax cable and the mounting mast are the 3rd and 4th dipole arm!

This will explain perfectly why the antenna has that erratic SWR curve. Googling a bit, I found a message from JA7UDA stating the antenna is really directive, with the main lobe just at the 50MHz radial direction. This was the confirmation for me that the antenna was really a no-balun V dipole on 50 MHz.

 V2000 simulation on MMANA. As you can see, the antenna's lobe is deformed at the 6m radial direction. This is the directivity noted by JA7UDE.

This situation can produce many effects, but for me the principals are:

1.- The antenna works randomly, It depends on the installation place, mounting hardware, coaxial cable, etc, etc...

2.- The polarization of the antenna is also random: Vertical at the radial direction, a mixture of vertical-horizontal at the others...

3.- A dipole without a balun makes the coaxial cable (and mounting hardware in this case) to radiate. This is a real problem!

As a experiment, I replaced all the antenna radials with full size quarter wavelength 50 MHz radials with the hope to convert it to a real ground plane antenna. The radials were made with aluminum tube, a M6 screw and a nut. The total length was 145 cm. More details at the next image:
The new radials in detail. This is only one of the multiples choices we have to make them. You can also tweak the antenna tuning adjusting their length. Make sure all three radials have the same length.

Results were much better than I could never expect. The SWR curve is now the one you can expect from a 50 MHz groundplane antenna: 1.00 at 51.080 and 1.4 at 50.000 and 52.000. But for me, the main advantage is the antenna now receives exclusively vertical polarization. This is a great advantage when you are located only 40 Km away from a 250 KW TV channel 2 transmitter!!! The previous TV noise of 9+ is now reduced to S1-S2, and now some real weak signal can be heard, like meteor reflections and multi-skip Es.

No changes were noticed in operation and performance on 2m and 70cm. Just as before the modification.

The modified V2000

If you have this antenna, and you are not happy with its performance, try to put a real ground plane as I described here. Its cost is under 15 euros and it works much (and much is much) better than the counterpoise.


On November 24, 2007 we were authorized to use the 50 MHz band, with the TV still on air, so the antenna helped a lot to work some interesting DX because of the high attenuation of the cross polarization. Later on April 9, 2010 the famous EA-TV transmitter (48.250 MHz) was turned off so the band become clean with just the usual urban noise. Using no more than 100W I have been able to work stations in north, middle and south Africa, Middle East, North and South America and of course, all Europe, so the antenna works as expected.

I also have received e-mails from other hams who had great success with the modification, but I received also some e-mails from hams who had very bad results from it.

Looking for "V2000" antenna in Internet, you can easily discover there are many "V2000" antennas, with some differences between them. Ones are single piece fiberglass, others are split in two pieces... Electrically most of them are quarter wavelength antennas (the one needed for this mod) but there are other who seems to be configured in a different electrical arrangement. On these antennas the mod does not produce any advantage. In fact it used to produce a lot of SWR and makes the antenna unusable.

What do I mean? There are many chances this modification could improve your V2000 antenna, but there still exists a possibility it will not work you your particular antenna. Anyway I encourage you to test the mod. If it works, the performance of your antenna will be much better. It will worth it.

For the curious, a single piece V2000 teardown can be found here.

Miguel A. Vallejo, EA4EOZ


  1. thank you for the article. 73 n1nq

  2. Hello, thank you for this blog post, I am going to try out this modification on a Watson W-2000. I would appreciate knowing how you fixed the M6 screw to the 8mm pipe and the 8mm pipe to the 6mm pipe. Also how long were you 8mm pipe sections?

    Thank you,


    1. The screw is embedded in the pipe by pressure. The same case for the 6mm pipe into the 8mm one. I used one meter long 8mm pipes and the rest up to the total radial length is 6mm pipe. Good luck with your modification!

    2. Nothing is easy! Do you know if this mod will work on a Diamond V2000? Looking at its photo, there appears to be a coupling or insulator about 1/3 the way up on the main radiator. Thanks for any info you can provide. John (WA3CAS)

    3. That is not an insulator. It is a loading coil.

  3. Have you checked for decent SWR on 10m after this mod? Even if only mediocre would prove to be a great base antenna for the 9800 radios.

    1. It doesn't work at all on 10m with or without the modification. Deaf as a doorknob.

  4. Comet GP-15 is a 5/8 on 6m.

    Nowhere (that I can find) does it claim to be the misleading "1/2" wave that the V2000 does :-)

    I almost bought a V2000 thinking it radiated as an end fed 1/2 wave on 6m, I quickly changed my mind once I learned it's really a 1/4 wave with one radial, and got a Comet GP-15, I also like that the GP-15 is a single piece antenna.

    I'm going to add full sized 1/4 wave radials to the GP-15 for 6m.

    Another thing to watch out for with a lot of these Diamond, Comet and friends antennas is the feedline is not properly decoupled from the antenna and will radiate/pickup noise/give finicky SWR readings etc - this isn't that noticeable on 2m and above, but at 6m it becomes an issue. Ferrite clamps or a decent current choke is recommended where the coax exits the base of the antenna.

  5. Also I have adapted the V2000 radials after reading your article. For a report with photos how I did it see:

  6. Estimado Miguel Ángel,

    Soy EA4AY Javier de Madrid. He leído tu artículo de la modificación de la Diamond V2000 (enhorabuena por el mismo, es muy interesante) y me gustaría, si me lo permites, hacerte tres preguntas. Tengo una Comet GP15 que se ha quedado totalmente sorda en 6m, probablemente se haya ido algún condensador. Quería preguntarte si me pudieras indicar si sabes la manera de abrir una Comet como esta es como las Diamond que al quitarle un tormillo en la base para puedes acceder a la antena interior de la fibra de vidrio, más que nada, como ya sabrás ,la Comet GP15 sólo es de un tramo. Por lo otro lado quería preguntarte si los componentes que lleva la V2000 son los mismos de los de la GP15 para proceder a su reparación, es decir, si me puedo basar en los componentes que has puesto en tu web de la V2000 para reparar la GP15. Y por último quería preguntarte si tu modificación de radiales de la V2000 es válida para la GP15 al ser antenas muy similares. ¡¡Muchísimas gracias!!

    73´s de EA4AY (Javier)

    1. Hola Javier. Nunca he visto una GP15 de cerca, pero no me cabe duda de que son antenas muy similares que se basan en el mismo principio, lo cual no quiere decir que usen los mismos valores de condensadores. No te va a quedar otra que abrirla y comparar. La modificacion de los radiales sí que debe ser efectiva en la GP15 ya que también viene con un radial sintonizable para 50 MHz. Suerte!

  7. I have a GP-15, Not happy with it at all. Crazy high SWR on 2 meter , don't know on 440, no analyzer. I'll try the 1/4 radials for 6 meter and see how it works. This has sat in a trailer for 4 years because of a couple moves. As soon as the new shack is done I'll get on this. Thank you

    1. I don't know what a GP-15 looks like inside but it should be very similar to the V2000, if not the same. Good luck!

    2. Diamond in there instruction sheet advise you to pace a one turn loop in the coax feed at the base of the antenna. This stabilises the issue with SWR problems on 6M

  8. Hola Miguel, tengo la intención de cambiar la V-2000, poniendo radiales para 6 metros. Para no tener demasiada resistencia al viento, y porque tengo 2 radiales con bobina (la 2da viene de una vieja V-2000) me gustaría saber qué crees que es diferente en las 2 opciones:
    1-Montar el V-2000 con 2 radiales con bobina y uno de 145 cm.
    2-Montar el V-2000 con 2 radiales con bobina y un radial de 50 cm. Eléctrica y prácticamente, ¿qué prevé, desde su experiencia?
    Muchas gracias, saludos, Maia, Portugal

    1. Hay que huir de los radiales con bobina. De hecho los que vienen con la V2000 ni siquiera son resonantes en 50 MHz.

  9. Agradecido por la claridad, ensayaré con los 3 radiales con 145 cm.

  10. Buenas tardes Miguel. Muchas gracias por tu aportación. Decirte que tengo montada una v2000 con tu modificación y va genial.
    El caso es que un colega me ha pedido realizarla a la suya con varilla de acero inox , y me encontrado con un problema.
    Empezando con las varillas a 150 y cortando poco a poco la roe mínima 1:1.15, se queda siempre en 52.300.
    No consigo bajar la frecuencia de roe mínima.
    He llegado a cortar hasta 135cm y sigue en la misma frecuencia 52.300.
    Podria tener incidencias cercanas o el cable coaxial
    Gracias por tus comentarios.


    1. Sí, algún problema con el coaxial o un problema de cercanía a otros objetos metálicos, como por ejemplo estar montada en un brazo en paralelo a la torre u otro mástil. Esto suele tener un efecto desastroso en la antena.

      Pero también puede ser que sea una antena diferente aunque por fuera parezca la misma antena por dentro puede ser eléctricamente otra antena distinta con una configuración de elementos distinta. Ya he visto varios casos de estos y a estas antenas los radiales no les hacen nada ya que no son cuartos de onda en 50 MHz.


  11. Ok.
    En principio es original.
    Tratare de elevarla y alejarla todo lo posible de todo.
    La Medida "estandar" del radial es 145cm
    Muchas gracias por todo

  12. Hi Miguel, the 8mm aluminium tubes that you put over the 6mm tubes, what length for the 8mm tubes have you used?

    1. The full tube (1 meter), and then the 6 mm one up to the 145 cm mark.

  13. I have managed to get a V2000 up today at a height of 10m on a steel mast. The SWR on 70cm and 6m is OK, but on 2m it is 2,2:1 on 145.500 MHz Any idea what to do to get the SWR on 2m lower?

    1. The antenna has no adjustments, so if SWR is high, and coaxial and connectors are fine, probably the antenna is defective. Try to check it using a second SWR meter, just in case... Good luck!