"dave" wrote in message
m...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.

Simple answer is no.

While you can build one with wirewound resistors , the normal formulars will
not usually work at RF and you will have a lot of inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.

Ralph Mowery wrote:
"dave" wrote in message
m...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.

Simple answer is no.

While you can build one with wirewound resistors , the normal formulars will
not usually work at RF and you will have a lot of inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.



Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

I need to lose about 5 dB from a 15 Watt exciter. Thanks.

Simple answer is no.

While you can build one with wirewound resistors , the normal formulars
will
not usually work at RF and you will have a lot of inductance to deal
with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.

Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

The reactance will change with frequency. Do you want to be fiddling with
antenna tuners? There is a whole lot of stuff you need to know when
designing and building. A good place to start is with an ARRL Handbook.
They can often be found in public libraries, but they are an excellent
reference on the subjects you are dealing with. I own several because even
the older information is useful.

In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

"Ian Jackson" wrote in message
...
In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

A bunch of chip resistors in parallel to ultimately make a T-atten.

In message , JB
writes

"Ian Jackson" wrote in message
...
In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

A bunch of chip resistors in parallel to ultimately make a T-atten.

Yebbut....
12W is a fair bit to dissipate with chip resistors (even a lot of them).
However, the question was if you could use WW resistors, not 'how to do
it properly'. I presume there was a reason why this was asked! After
all, we ARE talking 'amateur' radio.
--
Ian

In rec.radio.amateur.equipment Ian Jackson wrote:
In message , JB
writes

"Ian Jackson" wrote in message
...
In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

A bunch of chip resistors in parallel to ultimately make a T-atten.

Yebbut....
12W is a fair bit to dissipate with chip resistors (even a lot of them).
However, the question was if you could use WW resistors, not 'how to do
it properly'. I presume there was a reason why this was asked! After
all, we ARE talking 'amateur' radio.

A 5db T attenuator with 15 W in has the maximum dissipation in the shunt
resistor at about 5 W.

The input series resistor dissipates about 4 W and the output series
resistor dissipates a little over 1 W.

I see no reason to go to wirewound resistors at these power levels.


--
Jim Pennino

Remove .spam.sux to reply.

In message ,
writes
In rec.radio.amateur.equipment Ian Jackson
wrote:
In message , JB
writes

"Ian Jackson" wrote in message
...
In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

A bunch of chip resistors in parallel to ultimately make a T-atten.

Yebbut....
12W is a fair bit to dissipate with chip resistors (even a lot of them).
However, the question was if you could use WW resistors, not 'how to do
it properly'. I presume there was a reason why this was asked! After
all, we ARE talking 'amateur' radio.

A 5db T attenuator with 15 W in has the maximum dissipation in the shunt
resistor at about 5 W.

The input series resistor dissipates about 4 W and the output series
resistor dissipates a little over 1 W.

I see no reason to go to wirewound resistors at these power levels.

Oh, I quite agree. I wouldn't really choose to use WW myself, but I
think they would work in this application. It's just that I usually try
first to answer the question as asked, and, if necessary, start
embellishing things from then on!
http://www.youtube.com/watch?v=k7vMvlRio5Y&feature=related
--
Ian

wrote:


A 5db T attenuator with 15 W in has the maximum dissipation in the shunt
resistor at about 5 W.

The input series resistor dissipates about 4 W and the output series
resistor dissipates a little over 1 W.

I see no reason to go to wirewound resistors at these power levels.



What kind of 5 Watt resistors should I use?

Ian Jackson wrote:
In message , JB
writes

"Ian Jackson" wrote in message
...
In message , dave
writes
Ralph Mowery wrote:
"dave" wrote in message
news:0vqdnaEyq4zYAhfXnZ2dnUVZ_hJi4p2d@earthlink. com...
I need to lose about 5 dB from a 15 Watt exciter. Thanks.
Simple answer is no.
While you can build one with wirewound resistors , the normal
formulars will not usually work at RF and you will have a lot of
inductance to deal with.
Even the socalled non-inductive resistors are only so at the audio
frequencies.


Can the inductive reactance be cancelled with capacitors? I'm mainly
concerned with 40, 30 and 20 meters.

If your highest frequency is only 14MHz, and you're not trying to obtain
a sooper-dooper perfect match for your exciter, then I'd say that you
would certainly get away with using wirewound resistors.

To minimise the effects of the inductance, you could try mounting the
resistors 'hard down' against a ground plane. You might need a sheet of
some insulating material to avoid any danger of shorting to it.

And presumably, to get rid of 5dB (nearly 3/4 of your original 15W) you
intend to use paralleled-up resistors. This in itself will help minimise
the inductance.
--
Ian

A bunch of chip resistors in parallel to ultimately make a T-atten.

Yebbut....
12W is a fair bit to dissipate with chip resistors (even a lot of them).
However, the question was if you could use WW resistors, not 'how to do
it properly'. I presume there was a reason why this was asked! After
all, we ARE talking 'amateur' radio.

**** you.