Assembling Portsdown - Revision history

M0YDH: /* Mechanical Design */

2022-12-08T19:58:53Z

Mechanical Design

M0YDH: /* Mechanical Design */

2022-12-08T19:56:00Z

Mechanical Design

M0YDH: front panel model link

2022-12-08T19:30:26Z

front panel model link

M0YDH: /* Mechanical Design */

2022-08-12T13:21:56Z

Mechanical Design

M0YDH: /* Mechanical Design */ P2018 on 2 sides of a PCB

2022-08-12T13:20:25Z

Mechanical Design: P2018 on 2 sides of a PCB

M0YDH: /* Mechanical Design */ 3U 19 inch rack case

2022-08-12T13:01:25Z

Mechanical Design: 3U 19 inch rack case

G8PEF: /* Power Supplies and Wiring */

2019-10-05T21:14:26Z

Power Supplies and Wiring

G7UXW: Corrected URL from .tv to .org.uk

2019-01-07T14:54:40Z

Corrected URL from .tv to .org.uk

GI7UGV: Update a forum link to the new site.

2018-07-20T00:23:42Z

Update a forum link to the new site.

G8GKQ: /* Power Supplies and Wiring */

2017-12-03T16:35:58Z

Power Supplies and Wiring

@@ Line 11: / Line 11: @@
 The most difficult part will be to mount the Touchscreen display.  It can either be stacked on top of the RPi, or you can connect it by a short multiway lead and mount it on the front panel of your housing - an example is here:  http://www.ebay.co.uk/itm/141354697688.
-If you have a 3D printer you could try make up one of these housing http://www.thingiverse.com/thing:1920486
+If you have a 3D printer you could try make up one of these housing http://www.thingiverse.com/thing:1920486 . You will need a carved wooden packing piece between the back of the screen and the box front panel to support it.
 The Waveshare 3.5" touchscreens always seemed to fail during unit construction. If you must use one ask another member for a dead one to use as a template. Then fit your working one at the last minute into its bezel. The official RPi 7 inch touch screen is far superior and mounts well in a 3d printed bezel from a design available from G4XAT.

@@ Line 7: / Line 7: @@
 First of all, decide on your mechanical design.  You are going to need to have the RPi firmly mounted, with the Micro-SD card slot accessible (to change the card if required) and the power, network and USB connectors available.  Then you will need to stack a GPIO extender on top of the RPi. A secondhand 3U 19" rack case with mounting rails for vertical circuit cards may well be a good value purchase that is tall enough to take the 7 inch screen if you upgrade to Portsdown 2020 [Portsdown 3] later on. There will be enough room in this for a Minitioune receiver, 71MHz upconverter, all of the Portsdown 2018 hardware, a Lime Mini SDR, voltage converters and maybe some switch gear for amps.
-A front panel as CAD models for a 19 inch 3U box is here [[File:Portsdown_3_Front_Panel.zip]] in .dxf and .stp fprmats within a zip archive. The dxf could be printed full size and used as a cutting template.
+A front panel as CAD models for a 19 inch 3U box is here [[File:Portsdown_3_Front_Panel.zip]] in .dxf and .stp formats within a zip archive. The dxf could be printed full size and used as a cutting template.
-The most difficult part will be to mount the Touchscreen display.  It can either be stacked on top of the RPi, or you can connect it by a short multiway lead and mount it on the front panel of your housing - an example is here:  http://www.ebay.co.uk/itm/141354697688. The Waveshare 3.5" touchscreens always seemed to fail during unit construction. If you must use one ask another member for a dead one to use as a template. The official RPi 7 inch touch screen is far superior and mounts well in a 3d printed bezel from a design available from G4XAT.
+The most difficult part will be to mount the Touchscreen display.  It can either be stacked on top of the RPi, or you can connect it by a short multiway lead and mount it on the front panel of your housing - an example is here:  http://www.ebay.co.uk/itm/141354697688.
-f you have a 3D printer you could try make up one of these housing http://www.thingiverse.com/thing:1920486
+If you have a 3D printer you could try make up one of these housing http://www.thingiverse.com/thing:1920486
 You will then need to consider mounting the ADF4351 Synthesizer, any LO filters and then the Filter/modulator board.  Other things to think about might be a 5V power supply, a relay/PTT switching board and any dongles (EasyCap, Sound or RTL-SDR).

@@ Line 7: / Line 7: @@
 First of all, decide on your mechanical design.  You are going to need to have the RPi firmly mounted, with the Micro-SD card slot accessible (to change the card if required) and the power, network and USB connectors available.  Then you will need to stack a GPIO extender on top of the RPi. A secondhand 3U 19" rack case with mounting rails for vertical circuit cards may well be a good value purchase that is tall enough to take the 7 inch screen if you upgrade to Portsdown 2020 [Portsdown 3] later on. There will be enough room in this for a Minitioune receiver, 71MHz upconverter, all of the Portsdown 2018 hardware, a Lime Mini SDR, voltage converters and maybe some switch gear for amps.
-The most difficult part will be to mount the Touchscreen display.  It can either be stacked on top of the RPi, or you can connect it by a short multiway lead and mount it on the front panel of your housing - an example is here:  http://www.ebay.co.uk/itm/141354697688
+A front panel as CAD models for a 19 inch 3U box is here [[File:Portsdown_3_Front_Panel.zip]] in .dxf and .stp fprmats within a zip archive. The dxf could be printed full size and used as a cutting template.
 f you have a 3D printer you could try make up one of these housing http://www.thingiverse.com/thing:1920486

@@ Line 27: / Line 27: @@
 Here are the Portsdown 2018 cards in a Portsdown 2020 and next to the Pi3 - all in a 3U 19 inch rack case.
-[[File:P2020 M0YDH 02.jpg|600px]]
+[[File:P2020 M0YDH 02.jpg|600px]]  [[File:P2020 M0YDH 01.jpg|600px]]
 ===Interconnecting the modules===

← Older revision		Revision as of 13:20, 12 August 2022
Line 20:		Line 20:

	[[File:In the box.jpg\|600px]]		[[File:In the box.jpg\|600px]]
		+
		+	All the circuit cards for Portsdown 2018 except band decode and GPIO Breakout can be mounted on M3 stand-offs on both sides of a rectangle of plain PCB. A housing for a 25 way D connector can be constructed and soldered on. This has sufficient connections to take all the wiring across to the GPIO Breakout. RG402 semi-rigid coax and SMA fittings have been used with Molex KK connectors for the wiring. Pictures are from M0YDH.
		+
		+	[[File:P2020 M0YDH 03.jpg\|600px]] [[File:P2020 M0YDH 04.jpg\|600px]]
		+
		+	Here are the Portsdown 2018 cards in a Portsdown 2020 and next to the Pi3 - all in a 3U 19 inch rack case.
		+
		+	[[File:P2020 M0YDH 02.jpg\|600px]]

	===Interconnecting the modules===		===Interconnecting the modules===

@@ Line 59: / Line 59: @@
 Do not power unnecessary items from the RPi's 5v outputs on the GPIO connector.  Doing so will induce extra voltage drop in the input protection circuitry.  Power the VCO filter and RF Switch directly from the switch mode power supply.  No problems with ripple have been observed.
-  A lot of strange problems, such as the Portsdown running very slowly or intermittent/noisy streaming, can be caused by poor PSU volts - the RPi3 is actually specced for 5.1 volts, make sure your PSU delivers enough volts and current. See [https://forum.batc.org.uk/viewtopic.php?t=4856&p=11935#p11935 this post on the BATC forum] for a real user experience!
+  A lot of strange problems, such as the Portsdown running very slowly, can be caused by low PSU voltage - the RPi3 supply voltage is actually specified as 5.1 volts, so make sure your PSU delivers enough voltage and is capable of sourcing enough current. See [https://forum.batc.org.uk/viewtopic.php?t=4856&p=11935#p11935 this post on the BATC forum] for a real user experience!
 If you see a "Lightning Flash" symbol at the top right of your LCD display it means that the voltage at the RPi is too low.  You can measure the voltage between the GPIO connector pins 4 and 6.

@@ Line 83: / Line 83: @@
 The RPi camera gives excellent results, but only comes with a short ribbon cable to connect it to the RPi.
-It is possible to use some higher quality HDMI leads (the ground connections all need to be made) to extend the camera lead - this does NOT mean the signal out of the camera is HDMI, it is actually "Camera Serial Interface Type 2 (CSI-2)".   We are just using HDMI cable as a useful extension lead.  The modification described here https://wiki.batc.tv/CSI-2_to_HDMI allows the use of lower quality HDMI cables.
+It is possible to use some higher quality HDMI leads (the ground connections all need to be made) to extend the camera lead - this does NOT mean the signal out of the camera is HDMI, it is actually "Camera Serial Interface Type 2 (CSI-2)".   We are just using HDMI cable as a useful extension lead.  The modification described here https://wiki.batc.org.uk/CSI-2_to_HDMI allows the use of lower quality HDMI cables.
 Kits are available to connect a female HDMI connector to the RPi camera connector, and another female to the camera, allowing the use of domestic 1, 2 and 3m HDMI leads. The Pi camera HDMI Lead Extension Kit is available from here https://www.tindie.com/products/freto/pi-camera-hdmi-cable-extension/

@@ Line 71: / Line 71: @@
 An eBay buck regulator capable of supplying at least 4A continuous at 5.2V is recommended to power the RPi, an EasyCap, an RTL-SDR and the ADF4351.  '''Consumer-grade RPi power supplies with consumer grade USB cables have rarely proved to be capable of supplying this high demand without causing dropouts.'''
-The filter/modulator board needs a clean 5V at 250 mA and the on-board linear regulator supplies this, but can get warm at higher input voltages.  The linear regulator needs at least 7V to operate properly.  Feeding it with 8 volts provides th ebst compromise between regulator margin and heat dissipation.
+The filter/modulator board needs a clean 5V at 250 mA and the on-board linear regulator supplies this, but can get warm at higher input voltages.  The linear regulator needs at least 7V to operate properly.  Feeding it with 8 volts provides the best compromise between regulator margin and heat dissipation.
-You can use a buck converter to supply the filter-modulator board with 5V, but the switching ripple introduces some detectable sidebands on the transmitted signal. These have very little adverse effect, but are visible on a spectrum analyser.  On-board switching regulators have been tested, and the pads are there for L10 to provide extra filtering. Again, they introduce low-level sidebands, but these are probably not significant.
+You can use a switching or buck converter to supply the filter-modulator board with 5V, but the switching ripple introduces some detectable sidebands on the transmitted signal. These have very little adverse effect, but are visible on a spectrum analyser.  On-board switching regulators have been tested, and the pads are there for L10 to provide extra filtering. Again, they introduce low-level sidebands, but these are probably not significant.
 ===Network and USB Wiring===