Cecil Moore wrote:
Bill Turner wrote:
You didn't give many details such as the bandwidth of the antenna, but
if you use the NP0 type ceramic capacitors you should be ok. Loops,
especially small ones, are notorious for narrow bandwidth and stable
caps are a must.

I once used disc ceramic bypass caps to try to tune an
antenna. They went up in flames. For a small loop, I
would at least use doorknob quality caps.

Thanks to all for replies,
Actually my requirement is to pump 4W into 1meter diameter loop
antenna.
I need to tune the antenna to resonance 13.56Mhz and then match it.
I using some fixed capacitors and variable capacitors of small range
for fine tuning.
Now i am using ceramic fixed and ceramic variable capacitors and found
that its performance is good (I am not sure, the problem may in my
transceiver also).

I thinking of trying other capacitors, how about following combinations
mica fixed + mica variable
mica fixed + air variable

Is it worth to buy mica capacitors ?
can i simply buy mica capacitors ? , i found some vendors selling rf
mica capacitors ,
is there any big difference between them for HF frequency ?

regards,
palani