Can you use Silica gel packs - desiccants in Enclosures

[Anthony]

Hello SARA,

Question, are their issues using Silica gel packets (desiccants) inside enclosures for LNAs to help with removing moisture? Even with the addition of water drain holes in the enclosure, cryopumping. 

[Marcus D. Leech]

On 09/06/2024 14:33, Anthony wrote:

Hello SARA,

Question, are their issues using Silica gel packets (desiccants) inside enclosures for LNAs to help with removing moisture? Even with the addition of water drain holes in the enclosure, cryopumping.

Yup.  Of course, you have to revisit the enclosure on a regular basis to put/regenerated gel in place...

For larger enclosures, I've seen folks use these newfangled electronic dehumidifiers (based on peltier devices).

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[Anthony]

What also are your thoughts on adding a battery powered, Mini Hygrometer Thermometer Electronic Digital Humidity Meter Gauge inside the enclosures as well?

https://www.amazon.com/dp/B0CJRKWGK7?ref=ppx_yo2ov_dt_b_product_details&th=1

I'm also looking at what you referred Marcus, the peltier devices

https://www.google.com/search?q=peltier+devices&rlz=1C1VDKB_enUS930US930&sourceid=chrome&ie=UTF-8

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[Anthony]

Wouldn't the peltier device cause RFI with the LNA, unless you go battery powered?

On Sun, Jun 9, 2024 at 2:35 PM Marcus D. Leech <patchv...@gmail.com> wrote:

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[Marcus D. Leech]

On 09/06/2024 14:45, Anthony wrote:

Wouldn't the peltier device cause RFI with the LNA, unless you go battery powered?

It is kind of a crap-shoot, as for any electronic device with switching power supplies.

We use something like these in our motor cabin at the observatory:

https://www.amazon.ca/Dehumidifier-Homtronics-Dehumidifiers-One-Touch-Ultra-Quiet/dp/B0CHYSK2T8/ref=sr_1_11?crid=3GTJMEAQ4HEWW&dib=eyJ2IjoiMSJ9.lExHAK-ftr_r54bh9sblHx9tHFzSUxY4BXoAGWtuL_u-n4PrituSWeiH6nAeCXhs2B-d5xfe13O1QrsJj_tZVli34Jt84jbT_75-MfSkeLojrvIv-3lcjDDJkoHilC98N0PGf0wYG1eqw_a7GVg46HlucKfztrMn0_Jwik0fvn_tfQ2gERyXx9UduFAOSPBFErzrpf0m2VyqRgvsl0OA1_qcro0Y0Z-n9Yyj7dTncJg.hJLypqDFdQ0Eajq_p2z9ZUJ8qXRyDCdLEE7PErEN7rs&dib_tag=se&keywords=mini+dehumidifier&qid=1717958960&s=kitchen&sprefix=mini+dehumidifer%2Ckitchen%2C80&sr=1-11

The peltier device itself should be fine.  But there'll almost certainly be a switcher inside to drive the peltier device at 12V-24VDC.

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[Don Latham]

The Peltier devices need to be linear control. Almost all are bang-bang or switching servos. 

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From: "marcus leech" <patchv...@gmail.com>
To: "sara" <sara...@googlegroups.com>
Sent: Sunday, June 9, 2024 12:52:16 PM
Subject: Re: [SARA] Can you use Silica gel packs - desiccants in Enclosures

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------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

[Captain Anne Flint]

Hi Don,
Bang-Bang?
Wende

[Mike Otte]

Anthony,

1)  All electronics gives off heat. I am not sure of your LNA power usage but  5volts X .090A = .45 watt.  Leave the power on to keep the moisture out.

2)  On-Off control will give to you  twice.  NEvenoise turning on and off   and  oscillation of gain.

My 2 cents

Mike

On Sun, Jun 9, 2024 at 5:07 PM Captain Anne Flint <bera...@gmail.com> wrote:

Hi Don,
Bang-Bang?
Wende

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Mike Otte W9YS

[Anthony]

Hi Mike,

When I install the LNAs this weekend, leave the power on to keep the moisture out of the LNA housings and off the circuit boards?

In the past I would remove the power source and leave the LNAs until when needed. The LNAs are rated at minimum 9 DCV to a maximum of 15 DCV with a supply current of 8C mA. 

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[Alex P]

Anthony,

Rather than running the electronics constantly

add a continually powered 4W or so resistive heater to keep everything in the box  a few degrees above ambient.

Alex

[Douglas Decker]

I have worked on field devices outside for over 50 years. A heat strip with a thermocouple control will produce no noise and will attempt to maintain a steady temperature. In the south heat strips only work in the fall winter the sun does it the rest of the year. Most of the equipment we work on is rated for outdoor duty. LNS’s and SDR’a from Amazon are not. You have to design for extreme seasonal changes. My 2 Cents worth.

Sent from my iPhone

On Jun 10, 2024, at 8:15 AM, Anthony <itpart...@gmail.com> wrote:



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[Anthony]

I'll check for types and size, the LNA enclosures are: Dimensions - (internal): 8.4” x 4.4” x 2.3” inches (external) 9.5" x 5.8" x 2.8".

I may also do the same for the Cavity BPF, their enclosure Dimensions are: Inner Size of enclosure box(Approx.): 10.2" x 6.6" x 5.2"(258 x 167 x 132 mm)(L*W*H)

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[Anthony]

Hi Douglas, 

There are definitely extreme temperatures here. I've experienced replacing LNAs three times with all the rain and heavy humidity here in Roswell, GA USA. 

I am honestly tired of replacing LNAs due to humidity, especially in a short period of time. 

Something like this? Self-Adhesive Polyimide Flexible Heaters 302°F Max | Omega

Also, sealing up the end of the enclosures containing the LNAs with silicon works but I remember someone mentioning there are negative effects with using silicone to seal the openings where the coax is coming into the enclosures?

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[Anthony]

You always find such cool stuff, Alex!

I'm looking over them, thank you!

On Mon, Jun 10, 2024 at 10:16 AM 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

Heaters like this

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[b alex pettit jr]

 AND, if you want to maintain a specific temperature .. This Works

  I have been undertaking a several months long project to thermally stabilize a remote [at RT]  SDR 

Mission Accomplished .. will post the info this week.

Alex

[Anthony]

Nice!

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[b alex pettit jr]

Trying to keep a box Rain Sealed is a near impossibility

Better to choose the path by which pressure may be equalized , but without water being sucked in.

Consider something like this  ( size exaggerated for illustrative purposes ) 

Perhaps a 1/4" Red inner tube and 1" outer Blue tube fine.

[Lamar Owen]

On 6/9/24 14:35, Marcus D. Leech wrote:
> On 09/06/2024 14:33, Anthony wrote:
>> Hello SARA,
>>
>> Question, are their issues using Silica gel packets (desiccants)
>> inside enclosures for LNAs to help with removing moisture? Even with
>> the addition of water drain holes in the enclosure, cryopumping.
> Yup.  Of course, you have to revisit the enclosure on a regular basis
> to put/regenerated gel in place...
>
> For larger enclosures, I've seen folks use these newfangled electronic
> dehumidifiers (based on peltier devices).

Seems our DIRV project from a few years ago keeps being on-topic here....

For our two 26 meter instruments, six large peltier devices were
installed, Melcor/Laird model MAA600T-24 (
https://www.digikey.com/htmldatasheets/production/1829617/0/0/1/maa6x0t-xx-data-sheet.html
) using Oven Industries controllers.  The professors who were running
the DIRV project were extremely RFI-aware, and these systems met their
standards.  Each TE module is rated 600 BTU/hr, heating or cooling. 
Another unit was used to temperature control the LNA plate; the feed box
was kept to +/- 1 degree C, and the LNAs +/- 0.1 degree C.  As the DIRV
project's goal was simply keeping the LNA temperatures as constant and
thus the gains as stable as possible, humidity control was performed
using a typical industrial air dryer on a simple air-compressor driven
dry air system, piped to the feed box using air hose, I believe 3/4 inch ID.

For testing, the professors did indeed use large bags of silica gel
desiccant.  Changing them out in our feeds for recharge, requiring a
bucket truck operation, was rather unwieldy.

[Lamar Owen]

On 6/10/24 10:49, 'b alex pettit jr' via Society of Amateur Radio

Astronomers wrote:
>
> Trying to keep a box Rain Sealed is a near impossibility
>
> Better to choose the path by which pressure may be equalized , but
> without water being sucked in.

Indeed.  That's why our systems used the air compressor / air dryer
system that maintains positive pressure in the feed enclosure.

[Anthony]

Yep! I have two of those, smaller size for the BPF, but for the LNAs, I stuck with new fishing tackle boxes. 

The rain closure for the BPF are larger than I wish and it was a bit difficult figuring out how to attach them without using quite a bit of Ntype connector and "Elbow" connectors.

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[Anthony]

My setup is no where near that but I plan on keeping a watch on the enclosures to make sure moisture is monitored visually as well as through electronics.

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[Anthony]

My last LNAs, I thought were well sealed until the winter here with warms days, the freezing day, brought extreme conditions. When I pulled the fishing tackle boxes down and inspected them, there was quite a bit of water inside. I noticed my eastern LNA had more condensation than the western LNA enclosure.

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[Anthony]

I'm finishing up the work with the LNA & BPF enclosures. I've ordered the Adhesive plate heater and a temperature sensor with a waterproof enclosure.