开云体育

Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will work.

Let us know when you find that resistor.

Z

I suspect you would be better off with a 300 watt amplifier running closer to class A with transformer feed back, Most RF transistors have internal emitter resistors to balance the parallel cells. Making feedback work over a wide frequency range takes real talent and good pc board layouts. gfz

zerobeat40 wrote:

Alternative topologies, and using higher voltage devices make things
much easier. Common-emitter can be troublesome. We ended up going
common-drain (simple source followers), running 28V, and using a
diff-amp as the voltage gain stage, then resistive feedback to the
input stage. So, the feedback was DC to 100MHz or so. Ended up with
about 150W capability and IMD3 measured -58dBc rel one carrier. 5ths
and higher order were down substantially more.

We had tried simple xfmr feedback, problem was that the 2nd/4th/6th
order products, down near DC, were re-mixing with fundamentals to
create 3/5/7, etc. Weren't able to make xfmrs that operated close
enough to DC to get around that prob.

We worked with the semi mfr as well, trying to get internal resistors.
Turns out the technology used for emitter ballasting is fundamentally
non-linear. Good for balancing DC idle currents, but not very good
for negative feedback. In the MRF150 type devices, no such ballasting
is used, rather they depend on having 32 identical devices adjacent to
each other on a wafer, and bonding in direct parallel. Semiconductor
physics allows you to do things like that, expect adjacent devices to
be identical enough to directly parallel. In the MRF154, which was 4
X MRF150 in a single package, the drains and sources were in direct
parallel, and the only isolation resistors were in the gate paths,
cutting down on some form of cross-coupled VHF oscillation between
devices.

At one point, we feared we'd have an expensive hybrid design facing
us, but coming up with the diff-amp input, two stage buffer and final
output FETs, and getting the customer to buy off on 28V operation, did
the job. Complex circuit when we were done, and way more gain than
you want usually from a single stage, but we got the performance
without a custom hybrid design.

Hard to believe I was once in that industry...this was shore-based
marine SSB, we were supposed to meet a final system IMD of 36dBc rel
one carrier, including all stages...so we made them all super-clean,
and beat the spec by 10dB. Adjacent channel power measured far down
as well, but I don't recall the figure.

Actual torture test was to put band-limited white noise through it,
and see how much energy was in the next adjacent channel. A variation
on that test is still in use commercially, known as the "noise power
ratio" test.

Z

--- In ham_amplifiers@..., FRANCIS CARCIA <carcia@...> wrote:

I suspect you would be better off with a 300 watt amplifier running

closer to class A with transformer feed back, Most RF transistors have
internal emitter resistors to balance the parallel cells. Making
feedback work over a wide frequency range takes real talent and good
pc board layouts. gfz

zerobeat40 <zerobeat40@...> wrote: Hey, I tried to put the

NFB into a solid state amp once, being used as

a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will work.

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles me why
Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation for
cleanliness.

cheerz

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier running closer to class A with transformer feed back, Most RF transistors have internal emitter resistors to balance the parallel cells. Making feedback work over a wide frequency range takes real talent and good pc board layouts. gfz

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will work.

!. I would use 50v transistors.

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles me

why

Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation for
cleanliness.

cheerz

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier

running

closer to class A with transformer feed back, Most RF

transistors

RICH SEZ... I would use 50v transistors.

### Kinda tough in a mobile application... or some emergency
application where u use 12 vdc batteries, etc. These 50 vdc
finals don't seem to be much better than 30 vdc finals. I
believe there are some 70-100 v devices out there too.

### On another note.... some where I saw the specs for the common
transistor PA all these 11m ops use.. The manufacturer depicted a
graph of IMD vs power out in pep. Interesting, cuz the lower the
power out... the IMD just kept getting better.

### I still believe these 200 w xcvr's are the way to go... then
u can get a clean 50-150w out of them. Crank the idle current up
a bit... and watch the imd drop some more.

### There's no point in trying to achieve Class A specs like the
MK-V's I have.....at that point the xcvr is now better than the
linear amp behind it. The total systen IMD is gonna be the lesser
of the two. ..... unless u run the linear in class A.... which is
going to require a huge amount of anode dissipation. A sliding
bias scheme would be the ideal ticket... to minimize anode diss
during Class A. Krell does this with their Class A audio amps...
works too.

Later... Jim VE7RF

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles

me

why

Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation

for

cleanliness.

cheerz

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Nov 1, 2006, at 10:56 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier

running

closer to class A with transformer feed back, Most RF

transistors

RICH SEZ... I would use 50v transistors.

### Kinda tough in a mobile application...

3, YC--156s mobile. Roger that good buddy.

or some emergency
application where u use 12 vdc batteries, etc. These 50 vdc
finals don't seem to be much better than 30 vdc finals. I
believe there are some 70-100 v devices out there too.

I drive a car that uses a 208v battery.

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will
work.

!. I would use 50v transistors.

For 50V transistors operating at 100W per pair, the required resistor
is 0.8 ohms, wherein you'd need 0.8nH of inductance or less, still at
15 watts. Can you find that one? For MRF150s, it's 0.5 ohms, needing
less than 0.5nH of inductance, this time at 25 watts.

Let us know.

Z

On Nov 1, 2006, at 12:20 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will
work.

!. I would use 50v transistors.

For 50V transistors operating at 100W per pair, the required resistor
is 0.8 ohms, wherein you'd need 0.8nH of inductance or less, still at
15 watts. Can you find that one? For MRF150s, it's 0.5 ohms, needing
less than 0.5nH of inductance, this time at 25 watts.

Let us know.

Z

Do you have a FCC callsign?

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

RICH SEZ... Do you have a FCC callsign?

### He doesn't need one..... I don't have a FCC callsign either.
Check the master list.... a LOT of fellows with no callsigns... who
cares.

### some ZL remarked that having to take a CW exam was akin to
having to "shoe a horse" for a driver's exam. He's right of
course.

### Unless of course this is a conspiracy theory... and perhaps "Z"
is actually Rauch !! .... or maybe even Denny Haad.

later... Jim VE7RF

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 1, 2006, at 12:20 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@> wrote:
Hey, I tried to put the NFB into a solid state amp once, being
used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to
improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it
must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance
reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at
14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will
work.

!. I would use 50v transistors.

For 50V transistors operating at 100W per pair, the required resistor
is 0.8 ohms, wherein you'd need 0.8nH of inductance or less, still at
15 watts. Can you find that one? For MRF150s, it's 0.5 ohms, needing
less than 0.5nH of inductance, this time at 25 watts.

Let us know.

Z

Do you have a FCC callsign?

No, sir. Is that a requirement for inclusion in this group? I came
here to avoid the censorship of another group that looked down upon
those of us who were not licensed. If, however, this group is
similarly exclusionary, then please accept my apologies, and I shall
depart with what little grace I may have left.


Z

On Nov 1, 2006, at 3:38 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 1, 2006, at 12:20 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@> wrote:
Hey, I tried to put the NFB into a solid state amp once, being
used as
a driver for commercial HF SSB. It was not so easy....

Z

Do you have a FCC callsign?

No, sir. Is that a requirement for inclusion in this group?

Definitely Not. So why do you hide your name?

I came
here to avoid the censorship of another group that looked down upon
those of us who were not licensed.

He also looks down on those who do not agree with his technical missteps.

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Nov 1, 2006, at 12:47 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

RICH SEZ... Do you have a FCC callsign?

### He doesn't need one..... I don't have a FCC callsign either.

chortle

Check the master list.... a LOT of fellows with no callsigns... who
cares.

Charles Thomas Rauch, Jr.

### some ZL remarked that having to take a CW exam was akin to
having to "shoe a horse" for a driver's exam. He's right of
course.

### Unless of course this is a conspiracy theory... and perhaps "Z"
is actually Rauch !! .... or maybe even Denny Haad.

It can't be Rauch because he knows that the grid has to be positive with respect to the cathode in order for grid-current to flow.

later... Jim VE7RF





Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

It can't be Rauch because he knows that the grid has to be positive
with respect to the cathode in order for grid-current to flow.

Sounds like someone needs to review his basic tube theory.
Specifically, look up "contact potential bias".

Now, for the experiment.

Lay tube on bench. Any tube, as long as it works. Apply specified
filament/heater current. Place a high-Z voltmeter between the
cathode/fil and the control grid. Once the cathode warms up, what do
you read? Is the grid negative W.R.T. to cathode, or positive? Given
that the voltmeter has finite resistance, would you say that the grid
current is zero, or non-zero?

Connect a 100kohm resistor between grid and cathode. Measure the
potential difference between grid and cathode. Given that this
voltage is non-zero, is there grid current? What is the polarity of
the voltage?

The experiment is more dramatic with a transmitting tube. I don't
recall what the values will be for a 3-500Z, but I just ran through
some 4CX250Bs...typ voltage developed in the experiment is control
grid negative to cathode by 15-30 volts, with grid current flowing.

Let us know the results.

Z

Gidday Z,
Keep postin mate,callsigns dont matter, I don't post, just like to read an learn...just finnished me first amp an picking up tips for me next one...so keep em coming.
Cookie
zl4ad

On Nov 1, 2006, at 5:59 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

It can't be Rauch because he knows that the grid has to be positive
with respect to the cathode in order for grid-current to flow.

Sounds like someone needs to review his basic tube theory.
Specifically, look up "contact potential bias".

As I recall, the problem is that "Z" previously stated that, according to the characteristic curves, a 3-500Z(?) flows __mA of grid current when the grid-cathode potential is negative __V. According to the characteristic curves, grid current does not flow until the grid is positive.
Free, unsolicited advice: when you step in it, you can not succeed in hiding it from others - even if you are a discussion group "Administrator" who censors posts that discuss his misstatements.

Now, for the experiment.

Lay tube on bench. Any tube, as long as it works. Apply specified
filament/heater current. Place a high-Z voltmeter between the
cathode/fil and the control grid. Once the cathode warms up, what do
you read? Is the grid negative W.R.T. to cathode, or positive? Given
that the voltmeter has finite resistance, would you say that the grid
current is zero, or non-zero?

Connect a 100kohm resistor between grid and cathode. Measure the
potential difference between grid and cathode. Given that this
voltage is non-zero, is there grid current? What is the polarity of
the voltage?

The experiment is more dramatic with a transmitting tube. I don't
recall what the values will be for a 3-500Z, but I just ran through
some 4CX250Bs...typ voltage developed in the experiment is control
grid negative to cathode by 15-30 volts, with grid current flowing.

The only places where like charges attract are West Hollywood, Palm Springs, the Gay Bay (SF) et cetera.

Let us know the results.

he has a mouse in his pocket?

cheerz

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Z is slick... The bench test with just the filament heated fills the
tube with an electron cloud... The electrons have velocity... Some
will impact the grid and be captured... The grid will become more
negative and the excess electrons will flow from the grid to any less
negative point... Consider, that although we view the
filament/cathode to be negative it has electrons departing under
thermal acceleration which makes the filament structure itself less
negative...
I don't have the time at the moment but I will do a bench check on
some 4CX1000's that just happen to be hanging around under the bench
at the moment... I suspect that each individual element in the tube
will show voltage/current under Z's conditions..

denny / k8do

On Nov 2, 2006, at 6:58 AM, ad4hk2004 wrote:

Z is slick... The bench test with just the filament heated fills the
tube with an electron cloud... The electrons have velocity... Some
will impact the grid and be captured... The grid will become more
negative and the excess electrons will flow from the grid to any less
negative point...

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z
-------------------------
With +3 to +5 volts on the cathode, "about 20mA" does not flow. Zero grid current flows because the grid potential looks negative with respect to the cathode. .

Consider, that although we view the
filament/cathode to be negative it has electrons departing under
thermal acceleration which makes the filament structure itself less
negative...
I don't have the time at the moment but I will do a bench check on
some 4CX1000's that just happen to be hanging around under the bench
at the moment... I suspect that each individual element in the tube
will show voltage/current under Z's conditions..

With 3 to 5 volts negative on the grid, there should be "about 20mA" of grid current if Z is correct in this matter.

cheers

denny / k8do





Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem
is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction. As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

Please do not hesitate to point out errors and inconsistencies. There
are days when I am amazed that I remember which end of a fork to hold.


Z

I would expect, at that plate voltage and 3-5 volts bias you'd have significant ZSAC... but I'd think that grid current, if any, with no drive would be measured in microamps. True?

73, Tony W4ZT

zerobeat40 wrote:

Microamps is still not zero...Rich is claiming zero.

I think I measured fractional milliamps - e.g. hundreds of microamps.
May have to re-run the exp.

The 3-500Z is not a tube I have a lot of experience with, certainly
later in my career power levels of that nature would be handled with
silicon.

Z


--- In ham_amplifiers@..., Tony King - W4ZT
<w4zt-060920@...> wrote:

I would expect, at that plate voltage and 3-5 volts bias you'd have
significant ZSAC... but I'd think that grid current, if any, with no
drive would be measured in microamps. True?

73, Tony W4ZT

zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem
is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction. As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

Please do not hesitate to point out errors and inconsistencies. There
are days when I am amazed that I remember which end of a fork to hold.


Z