[HamWAN PSDR] The 3rd time is not charmed [was: 8dB drop/rise!]

[Dean Gibson AE7Q]

On 2014-07-21 16:06, Dean Gibson AE7Q wrote:
> On 2014-07-21 11:26, Tom Hayward wrote:
>> This is a great deal for anyone who needs a HamWAN client.  
>> Resurrecting the modem is probably a 10 minutes job, and these 
>> Poynting antennas are sold out everywhere.
>>
>> Tom KD7LXL
>
> Thanks for the info about NetInstall, but when I hold the reset button 
> on the 5SHPn, it stops flashing after about 15 seconds, which 
> according to the documentation is the supposed acknowledgment that it 
> is going to search for NetInstall for a PXE boot.
>
> NetInstall has the PXE server enabled, but never sees the 5SHPn.
>
> Yes, $120 is a good deal for the package.

Having not received any offers for my "great deal", I began to wonder 
why the 5SHPn clearly is decoding pressing the reset button (by its 
flashing pattern), but then not interrogating "NetInstall" for the PXE 
boot.  So, I decided to read up on PXE boot (NOT on the MicroTik site).

I discovered that the "normal" PXE protocol starts out using DHCP, but I 
was never seeing the result of a DHCP-assigned IP address (and of course 
no response to access via the MAC address).  So, I decided to go look in 
my DHCP server logs.  I saw (and expected) DHCPDISCOVER / DHCPOFFER 
sequences prior to the failure, but after the failure, I was surprised 
to see BOOTREQUEST / BOOTREPLY sequences (with the appropriate IP 
address!) when trying to PXE boot.  BOOTREQUEST / BOOTREPLY sequences 
are part of the old BOOTP protocol (before DHCP was invented).

According to Wikipedia, *PXE normally uses DHCP, but the 5SHPn is using 
the old BOOTP protocol for PXE*.  Since DHCP servers normally respond 
(for compatibility purposes) to BOOTP requests as well as DHCP requests, 
it appeared that my DHCP server was responding to the 5SHPn before the 
MikroTik "NetInstall" could, and since the former was not configured to 
send the 5SHPn a boot file, nothing happened.

So, I temporarily disabled my DHCP servers, and voila!  NetInstall 
laboriously (meaning very slowly) installed a new copy of the firmware.  
I did my usual reconfiguration script, and I was up and running, albeit 
with the 8dB loss.

The first two instances of the 8dB drop were rather sudden, but the 
latest drop occurred over a period of about two weeks, which made me 
suspect vegetation growth as well as a problem with the 5SHP.  So, I 
decided to engage in another antenna aiming session, and that seems to 
have recovered about 5dB of the drop.

Bart: "/interface wireless monitor 0" shows "band: 5ghz-n-5mhz".  I 
presume that means I'm using a 5MHz link?


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