Using HF dummy load in VHF and UHF

[fjpompeo]

Hi,

I build a dummy load using 20 resitors of 1k ohm x 2W carbon in parallel. In HF it works OK. can I use the same load in VHF or UHF? My radio is an YAESU FT-857D.

73,

Fernando - PU2PLL - BRAZIL

 

[IanP]

Re: VHF Dummy Load

If it is done in similar way as in the link below, I can't see any reason why not ..

**broken link removed**

Rgds,
IanP

 

[BigBoss]

VHF Dummy Load

At UHF frequencies, it won't work due to leads of the resistors.

 

[karesz]

VHF Dummy Load

You see, so 30 years age didnt exist SMD parts, but VHF circuits yes...
Clear, its better if we dont have (much) parasitics, but "leadless is not over all & the only one"
K.

 

[IanP]

Re: VHF Dummy Load

At UHF frequencies, it won't work due to leads of the resistors.

Everything has leads ..

I don't think there is anything wrong with this load .. see attached picture ..
:idea:

 

[pranam77]

VHF Dummy Load

Yes it should work without any problems. But do remember to keep all leads as small as possible...Cheers

 

[vfone]

Re: VHF Dummy Load

The dissipated power of your dummy-load will be in the best case 40W, actually would be less than this due to the temperature interaction between resistors.

Beware that 857 have 50W in VHF, and could burn your resistors if you use for long time FM at full power.

Burning some of the resistors doesn't cost you too much, but the overall resistance of the load will go up from 50 ohms, placing in danger the 857 VHF power amplifier.

73's

 

[karesz]

VHF Dummy Load

Hi vfone,
40W isnt so away from 50W output power, so I think for short time & eventuelly in some oil coolant it must be really not a problem.
Otherwise its surly better to apply i.e.24x 1K2 or 30x 1K5 a 2W...
73 de Karesz

 

[steve_rb]

Re: VHF Dummy Load

I need to make a 3Kw (13.56 Mhz) 50 ohm dummy load. Any advice how to make a cheap and raliable one with standard radiation?

 

[karesz]

VHF Dummy Load

HI,
for some idea-orientation (& google pls): www.qsl.net/iz7ath/web/02_brew/15_lab/03_dummy/pag01_eng.htm
www.dj4uf.de/projekt/dummyload/dummyload.html
1800W-up to 3KW, homebrowed: www.mods-ham.com/03_Home-brew/Dummyload.pdf
K.