It depends some what on the fan construction, but generally the stacked
fans should be capable of a higher pressure at roughly the same air
flow. When the flow is restricted as it would be with the tiny 4CX-250s
the amount of air would be notably increased. Unfortunately there is no
way to know how much change you will get when stacking fans like that.
It's more a "do it" and then "measure the change". The specs are around
some where that will give the flow through a given tube for a given back
pressure assuming there are no leaks in the compartment. It's easy to
build a U-tube manometer to measure the back pressure in inches of water
just using some clear plastic tubing of a 1/4 to 3/8" diameter. The
construction was in the older Handbooks and may still be in them or the
book on classic amp design.
73
Roger (K8RI)
donroden@hiwaay.net wrote:
> I used stacked muffin fans on a 4 x 4CX250 amp, and one fan wouldn't
> get the job done. Two worked great, and three didn't seem to be
> proportionally better.
> Don WA4NPL
>
>
>
>
> Quoting vk3pa@vk3pa.com:
>
>
>> Quoting James Colville <jimw7ry@gmail.com>:
>> EMTRON uses 2 fans one under the tube blowing es the other a pc type
>> fan on top
>> sucking..
>>
>>
>>
>>> Fans in series? How are you going to figure the airflow out? Just use a
>>> single BLOWER like 100% of the other amp builders use? What tube or tubes?
>>>
>>> 73
>>> Jim W7RY
>>>
>>>
>>>
>>> On Mon, Jan 25, 2010 at 12:28 PM, MIKE DURKIN <patriot121@msn.com> wrote:
>>>
>>>
>>>> Ok, yea its not for VHF, Just HF but was thinking about parasitics and all
>>>> ....
>>>>
>>>>
>>>>
>>>> Next thought is there a rule of thumb when stacking fans back-to-back to
>>>> figure CFM and pressure ....
>>>>
>>>> Like if i had 2 fans with 98.1CFM/0.28" blowing in series?
>>>>
>>>>
>>>>
>>>> Mike
>>>>
>>>> KC7NOA
>>>>
>>>>
>>>>
>>>>
>>>> snip>
>>>>
>>>>> Hi Mike,
>>>>>
>>>>>
>>>>>> I'm wanting to supply the tube on one side of the tube and put the
>>>>>>
>>>> blocking cap for the C.L.C. output
>>>>
>>>>> about 110Deg off around the tube. Will that make for any internal issues
>>>>>
>>>> ETC. from
>>>>
>>>>> misbalance on the Anode ??
>>>>>
>>>>> If I understand you correctly, looking down at the tube, the HV supply
>>>>>
>>>> (connection to
>>>>
>>>>> the anode RF choke) is at 12 o'clock, and the blocking capacitor to the
>>>>>
>>>> output tank
>>>>
>>>>> comes off at about 4 o'clock (or 8 o'clock). If that's what you mean,
>>>>>
>>>> that should be
>>>>
>>>>> fine. (Unless you're working at VHF or UHF frequencies... then I don't
>>>>>
>>>> have a clue as
>>>>
>>>>> to whether it's OK.)
>>>>>
>>>>> 73,
>>>>>
>>>>>
>>>>>
>>>>> George T Daughters, K6GT
>>>>> CU in the California QSO Party (CQP)
>>>>> October 2-3, 2010
>>>>>
>>>>>
>>>>>
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