"exray" wrote in message
...
I've got a cheapo CB swr meter which I thought might be suitable for
some HF QRP work. Problem is that it is very insensitive on the HF
freqs. Can't even get more than about 20% of the scale with 5 watts on
40 meters.

It uses a stripline for pickup and I'm wondering if maybe I should
replace that with a broadband toroid configuration. Any specific
recommendations? How about adding some gimmick capacitance across the
stripline to increase coupling?

TIA,
Bill WX4A

You might find they used 1n4148 diodes just to be cheap. Try Germanium like
1n270.

I built one out of the Handbook back in the 70's they called the Monimatch
using a circuit board stripline. It was easy to cut rather than etching. I
don't remember the year.

In the 78 issue there is one as you describe. The broadband torroid sensors
are about standard in the autotuners and in some radios because they tune up
at low power. They are small and don't add much inductance. You might even
build it into a qrp rig and use a multi function meter scrapped out of an
old tape recorder or a led bar graph.

In the 78 issue there is one as you describe. The broadband torroid sensors
are about standard in the autotuners and in some radios because they tune up
at low power. They are small and don't add much inductance. You might even
build it into a qrp rig and use a multi function meter scrapped out of an
old tape recorder or a led bar graph.
================================
High intensity LEDs (for example those as used in traffic lights ,225 ea
per light) already light-up at 45 microampere and hence can be directly
used as a reflected power indicator instead of a meter.

Frank KN6WH

On Nov 23, 10:07*am, highlandham wrote:
In the 78 issue there is one as you describe. *The broadband torroid sensors
are about standard in the autotuners and in some radios because they tune up
at low power. *They are small and don't add much inductance. *You might even
build it into a qrp rig and use a multi function meter scrapped out of an
old tape recorder or a led bar graph.

================================
High intensity LEDs (for example those as used in traffic lights ,225 ea
per light) already light-up at 45 microampere and hence can be directly
used as a reflected power indicator instead of a meter.

Frank * KN6WH

Cool idea, Frank! Should work fine at low frequencies, but beware
that the junction capacitance of high power LEDs can be pretty high so
they likely wouldn't be great at higher frequencies. I just measured
some low power ones a few days ago at about 20pF, which is about 265
ohms reactance at 30MHz, not bad at all, but wouldn't be so good at
450MHz.

Cheers,
Tom

On Nov 23, 7:56 pm, K7ITM wrote:
On Nov 23, 10:07 am, highlandham wrote:

In the 78 issue there is one as you describe. The broadband torroid sensors
are about standard in the autotuners and in some radios because they tune up
at low power. They are small and don't add much inductance. You might even
build it into a qrp rig and use a multi function meter scrapped out of an
old tape recorder or a led bar graph.

================================
High intensity LEDs (for example those as used in traffic lights ,225 ea
per light) already light-up at 45 microampere and hence can be directly
used as a reflected power indicator instead of a meter.

Frank KN6WH

Cool idea, Frank! Should work fine at low frequencies, but beware
that the junction capacitance of high power LEDs can be pretty high so
they likely wouldn't be great at higher frequencies. I just measured
some low power ones a few days ago at about 20pF, which is about 265
ohms reactance at 30MHz, not bad at all, but wouldn't be so good at
450MHz.

Cheers,
Tom

I'm a looking at my tentec 1202 swr kit I a built. They usin' dual
stacked iron toroids just large enough ID to pass an inch long piece
of RG174 coax and 10 turns of 26 AWG enamel wire.

raypsi wrote:


I'm a looking at my tentec 1202 swr kit I a built. They usin' dual
stacked iron toroids just large enough ID to pass an inch long piece
of RG174 coax and 10 turns of 26 AWG enamel wire.

Thanks everybody, that seems to be the way to go.

73,
Bill - WX4A

On Nov 23, 1:07*pm, highlandham wrote:
In the 78 issue there is one as you describe. *The broadband torroid sensors
are about standard in the autotuners and in some radios because they tune up
at low power. *They are small and don't add much inductance. *You might even
build it into a qrp rig and use a multi function meter scrapped out of an
old tape recorder or a led bar graph.

================================
High intensity LEDs (for example those as used in traffic lights ,225 ea
per light) already light-up at 45 microampere and hence can be directly
used as a reflected power indicator instead of a meter.

Problem is, you don't get any visual output until the 1.6V biases the
LED, much higher than a germanium or silicon detector diode in a
traditional bridge. Some of the high-efficiency LED's are even higher
forward voltage drops, and can exhibit weird visual hysteresis effects
too at low current - meaning that they turn on at some current but
don't turn off until a much lower current.

Many QRP'ers use a clever idea of using an auditory output from the
bridge. For example Fig 7.46 in EMRFD. Works very well in night-time
QRP'ing, and tuning to reduce the squeal is incredibly intuitive.

Tim N3QE